A zone plate is found to give series of images of a point source on its axis. If the strongest and the second strongest images are at distances of 0.30m and 0.06 m respectively from the zone plate (both from the same side remote from the source), calculate the distance of the source from the zone plate, principal focal length and the radius of the second zone. Assume λ = 6 x 10-7m. ​

Answers

Answer 1
Hi have a wonderful day GOD love you

Related Questions

describe the importance of the neutron in a atomic nuclei ​

Answers

Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen nucleus. Neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes.

Hope it helps!

Neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons can explain the phenomenon of isotopes (same atomic number with different atomic mass). The main role of neutrons is to reduce electrostatic repulsion inside the nucleus.

Diffusion and osmosis are forms of passive transport.

True
False

Answers

Answer:

True. Diffusion and osmosis are forms of passive transport.

Explanation:

In diffusion, particles move from an area of higher concentration to one of lower concentration until equilibrium is reached.

In osmosis, a semipermeable membrane is present, so only the solvent molecules are free to move to equalize concentration.

Answer:

100% true

Explanation:

Simple diffusion and osmosis are both forms of passive transport and require none of the cell's ATP energy. Example of diffusion: Gas Exchange A biological example of diffusion is the gas exchange that occurs during respiration within the human body.

4. A disobedient student dropped his Physics textbook (mass 0.1kg) from the window (15m above the ground). How fast was it going when it hit the ground?

Answers

Answer:

v= 17.15 m/s

Explanation:

mass of the book=0.1 Kg

height above ground, h= 15 m

Using conservation of energy

Potential energy is converted into kinetic energy

[tex]mgh = \frac{1}{2}mv^2[/tex]

[tex]v=\sqrt{2gh}[/tex]

[tex]v=\sqrt{2\times 9.8\times 15}[/tex]

[tex]v=\sqrt{294}[/tex]

v= 17.15 m/s

Hence, the book will hit the ground at the speed of 17.15 m/s.

Calculate the volume of 1280 kilograms of aluminium if the density is 2700kg/m3

Answers

Answer:

0.47m3

Explanation:

Volume = Mass / Density

In this case:

Mass - 1280 kg

Density - 2700kg/m3

1280 / 2700 = 0.4740741m3

When this is rounded off ( 2 d.p ):

0.47 m3

HOPE THIS HELPED

A woman does 236 J of work
dragging her trash can 24.4 m to
the curb, using a force of 18.9 N.
At what angle was her force
directed?

Answers

Answer:

workdone = force × distance 236J = 18.9cos(o) × 24.4236/24.4 = 18.9cos(o)(0.5117)cos^-1 = (o)59.21°

a 45 kg boy sits on a horse on a carousel 5.0 m from the center of the circle. he makes a revolution every 8.0 s.
calculate his speed.
what is centripetal force acting on the boy?​

Answers

For every complete revolution the boy makes around the center of the carousel, he travels a distance of 2π (5.0 m) = 10π m, which gives a linear speed of

v = (10π m) / (8.0 s) ≈ 3.927 m/s

Then his centripetal acceleration would be

a = v ² / (5.0 m) ≈ 3.084 m/s²

so that the centripetal force exerted on him has magnitude

F = (45 kg) a ≈ 138.791 N ≈ 140 N

(rounded to 2 significant digits)

le Which describes how light waves can interact with wood?
(14 Points)

O A. absorption and reflection
O B. diffraction and transmission
0 C. reflection and refraction
O D. transmission and refraction​

Answers

Answer: A ,absorption and reflection

Explanation

Absorption and reflection are the two phenomena which describe how the light waves can interact with the wood. Thus, the correct option is A.

What is Absorption and reflection of light?

Light absorption is a process through which light is absorbed and converted into different form of energy. An example of absorption of light is the process of photosynthesis which takes place in plants. However, light absorption does not occur exclusively in the plants, but in all the creatures and inorganic substances present on this planet.

When a ray of light approaches a smooth polished surface such as a metal surface and the light ray bounces back, it is called as the reflection of light. The incident light ray which lands on the surface is reflected off the surface. The ray that bounces back from the surface is called the reflected ray.


Therefore, the correct option is A.

Learn more about Light waves here:

https://brainly.com/question/23460034

#SPJ6

please help thank you ​

Answers

YOUR QUERY :

which of the following statements BEST describes the difference between an atom and an ion ?

Answer:

well the correct answer is

d. An atom contains equal numbers of protons and electrons whereas an ion contains unequal numbers of protons and electrons .

Explanation:

A charged atom is known as an ion, well it can be negative as well as positive charge.

if atom has more protons than electrons then it get positively charged and known as cation

if the atom has more electrons that the number of protons then the atom get negatively charged and known as anion

A football player kicks a ball with a mass of 0.5 kg. The average acceleration of the football was 15 m/s/s. How much force did the kicker apply to the football?

A. 15.5 N
B. 7.5 N
C. 14.5 N
D. 30 N

Answers

Answer:

Explanation:

F = m*a = (0.5)*15 = 7.5 N

A 4 kg bowling bowl is sitting on a table 1 meter off the ground. How much potential energy does it have?

Answers

Answer:

[tex]\huge\boxed{\sf P.E. = 39.2\ Joules}[/tex]

Explanation:

Given Data:

Mass = m = 4 kg

Acceleration due to gravity = g = 9.8 m/s²

Height = h = 1 m

Required:

Potential Energy = P.E. = ?

Formula:

P.E. = mgh

Solution:

P.E. = (4)(9.8)(1)

P.E. = 39.2 Joules

[tex]\rule[225]{225}{2}[/tex]

Hope this helped!

~AH1807

Stand in a doorway so your toes and nose are against the doorway. 4. Grab a weight in each hand and hold your arms out from your body on either side of the wall. 5. Try to stand on your tip toes. What happens

Answers

You are unable to fully stand up because you can’t lean forward and center your center of gravity below you (door frame prevents you)

What is the force needed to accelerate a 10 kg object at 2 m/s??​

Answers

Answer:

5 newtons

Explanation:

Just divide them

Create a following distance greater than 3 seconds ahead when_______. a driver behind you is trying to pass you are not in a hurry there is no traffic on the road you are traveling in front of a motorcycle.

Answers

Answer:

option (a)

Explanation:

Maintaining distance while driving in traffic can avoid the chances of an accident.                        

When the driver is behind you is trying to pass you to avoid the collision you should maintain a distance greater than 3 sec.

Hence, option (a) is correct.

 

Answer:

a driver behind your vehicle is trying to pass you

Explanation:

took test and checked

Victor covers 210 km by car at a speed of 70 km/hr. find the time taken to cover this distance.

Answers

Answer:

3 hrs

Explanation:

the distance covered by victor= 210 km

speed= 70 km/hrs

so, 70×3= 210

so the answer is 3 hrs

BTW im a small kid so don't just right away say the explanation sucks and the subject physics is not yet started in my grade.

edit: don't give me brainless answer plz.

A 9.0 × 10 3 kg satellite orbits the earth at the distance of 2.56 × 10 7 m from Earth's surface. What is its period?

Answers

Answer:

1.6537 * 10^9

Explanation:

Given that :

Distance (r) = 2.56 × 10^7 m

Using the relation from Kepler's third law of motion :

T2 = [ 4* pi^2/ G (M1 + M2) ]r^3

M1 = mass of earth = 5.97 *10^24

M2 = Mass of satellite = 9.0 × 10^3 kg

G = Gravitational constant = 6.67 *10^-11

T2 = [ (4 x 3.14^2) / 6.67 x 10^-11 ( 9 x 10^3 + 5.97 x 10^24)]/ (2.56 x 10^7)^3

= 1.6537 * 10^9

What 2 factors do you need in order to calculate speed?

Answers

Answer:

Distance and time.

Explanation:

Speed=Distance/time

The two factors which we need in order to calculate the speed of an object are the distance covered by the object and the time taken to cover that distance.

What is Speed?

Speed is the rate of change of position of an object in any direction. Speed is a scalar quantity as it has only magnitude and no direction. It is measured as the ratio of the distance covered by an object to the time taken in which the distance was covered by that object.

Speed has the dimension of distance covered by the time taken. Thus, the SI unit of speed is the combination of the basic units of distance and the basic unit of Time. Thus, the SI unit of speed is meter per second (m/s).

Learn more about Speed here:

https://brainly.com/question/28224010

#SPJ6

A circular space station of radius 100 m rotates twice each minute.

a. Find the acceleration of an astronaut standing at the outer edge of the space

station. How many g's does she feel? (1g=9.8ms2)

b. What must the period of rotation of the space station be in order for astronauts

at the outer edge to experience the same acceleration as on earth?​

Answers

The space station completes 2 revolutions each minute, so that it traverses a distance of 2π (100 m) = 200π m each minute, giving it a linear/tangential speed of

v = (200π m) / (60 s) ≈ 10.472 m/s

(a) The astronaut would experience an acceleration of

a = v ² / (100 m) ≈ 1.09662 m/s² ≈ 0.1119g0.11g

(b) Now you want to find the period T such that a = g. This would mean the astronaut has a tangential speed of

v = (200π m) / T

so that her centripetal/radial acceleration would match g :

a = g = ((200π m) / T )² / (100 m)

Solve for T :

(100 m) g = (400π ² m²) / T ²

T ² = (400π ² m²) / ((100 m) g) = (4π ² m)/g

T = √((4π ² m) / (9.8 m/s²)) ≈ 2π √(0.102 s²) ≈ 2.007 s ≈ 2.0 s

What happens at the end of most cold currents?​

Answers

Answer:

Ocean currents act as conveyer belts of warm and cold water, sending heat toward the polar regions and helping tropical areas cool off, thus influencing both weather and climate.

Explanation:


If ocean currents were to stop, climate could change quite significantly, particularly in Europe and countries in the North Atlantic. In these countries, temperatures would drop, affecting humans as well as plants and animals. In turn, economies could also be affected, particularly those that involve agriculture.

A car travels through a valley at constant speed, though not at constant velocity. Explain how this is possible.

Answers

Answer:

Explanation:

An object following a circular path can be covering the same distance along the circle's circumference with every passing minute, giving it a constant speed. Since a change in either speed OR direction means a change in velocity, the object's velocity is not constant.

velocity is a vector so therefore direction affects it being constant.

An object's acceleration is the rate its velocity (speed and direction) changes. Therefore, an object can accelerate even if its speed is constant - if its direction changes. If an object's velocity is constant, however, its acceleration will be zero.  

Velocity is a vector so therefore direction affects it being constant.

What is velocity?

When an item is moving, its velocity is the rate at which its direction is changing as seen from a certain point of view and as measured by a specific unit of time

An object following a circular path can be covering the same distance along the circle's circumference with every passing minute, giving it a constant speed. Since a change in either speed OR direction means a change in velocity, the object's velocity is not constant. An object's acceleration is the rate its velocity (speed and direction) changes. Therefore, an object can accelerate even if its speed is constant - if its direction changes. If an object's velocity is constant, however, its acceleration will be zero.  

Velocity is a vector so therefore direction affects it being constant.

To learn more about velocity refer to the link

brainly.com/question/18084516  

#SPJ6

4. What is the electric field strength (E) at a distance of 0.50 m from a 1.00×10°C charge?

Answers

Answer:

3.6*10¹⁰N/C

Explanation:

The formula for Electric field strength is expressed as:

E = kQ/r²

k is the coulombs constant = 9*10^9Nm²/C²

Q is the charge = 1.00×10°C

r is the distance = 0.50m

Substitute the parameters into the formula as shown:

E = kQ/r²

E =  9*10^9(1)/0.5²

E =  9*10^9/0.25

E = 36*10^9

E = 3.6*10¹⁰N/C

Hence  the electric field strength is 3.6*10¹⁰N/C

A uniform rod is hung at one end and is partially submerged in water. If the density of the rod is 5/9 that of water, find the fraction of the length of the rod above water

Answers

Answer:

[tex]\frac{y}{L}[/tex] = 0.66

Hence, the fraction of the length of the rod above water = [tex]\frac{y}{L}[/tex] = 0.66

and fraction of the length of the rod submerged in water = 1 - [tex]\frac{y}{L}[/tex] = 1 - 0.66 = 0.34  

Explanation:

Data given:

Density of the rod = 5/9 of the density of the water.

Let's denote density of Water with w

And density of rod with r

So,

r = 5/9 x w

Required:

Fraction of the length of the rod above water.

Let's denote total length of the rod with L

and length of the rod above with = y

Let's denote the density of rod = r

And density of water = w

So, the required is:

Fraction of the length of the rod above water = y/L

y/L = ?

In order to find this, we first need to find out the all type of forces acting upon the rod.

We know that, a body will come to equilibrium if the net torque acting upon a body is zero.

As, we know

F = ma

Density = m/v

m = Density x volume

Volume = Area x length = X ( L-y)

So, let's say X is the area of the cross section of the rod, so the forces acting upon it are:

F = mg

F = (Density x volume) x g

g = gravitational acceleration

F1 = X(L-y) x w x g (Force on the length of the rod submerged in water)

where,

X (L-y) = volume

w = density of water.

Another force acting upon it is:

F = mg

F2 =  X x L x r x g

Now, the torques acting upon the body:

T1 + T2 = 0

F1 ( y + [tex](\frac{L-y}{2})[/tex] ) g sinФ - F2 x ([tex]\frac{L}{2}[/tex]) x gsinФ = 0

plug in the  equations of F1 and F2 into the above equation and after simplification, we get:

[tex](L^{2} - y^{2} ) . w[/tex] = [tex]L^{2}[/tex] . r

where, w is the density of water and r is the density of rod.

As we know that,

r = 5/9 x w

So,

[tex](L^{2} - y^{2} ) . w[/tex] = [tex]L^{2}[/tex] . 5/9 x w

Hence,

[tex](L^{2} - y^{2} )[/tex] = [tex]\frac{5L^{2} }{9}[/tex]

[tex]\frac{L^{2} - y^{2} }{L^{2} }[/tex] = [tex]\frac{5}{9}[/tex]

Taking [tex]L^{2}[/tex] common and solving for [tex]\frac{y}{L}[/tex], we will get

[tex]\frac{y}{L}[/tex] = 0.66

Hence, the fraction of the length of the rod above water = [tex]\frac{y}{L}[/tex] = 0.66

and fraction of the length of the rod submerged in water = 1 - [tex]\frac{y}{L}[/tex] = 1 - 0.66 = 0.34

A block of mass m is hung from the ceiling by the system of massless springs consisting of two layers. The upper layer consists of 3 strings in paralle, and the lower layer consists of 2 strings in parallel. The horizontal bar between the two layers has negligible mass. The force constants of all springs are k. Calculate the period of the vertical oscillations of the block.

Answers

Answer:

  T₀ = 2π [tex]\sqrt{\frac{m}{k} }[/tex]           T = [tex]\sqrt{\frac{5}{6} }[/tex] T₀

Explanation:

When the block is oscillating it forms a simple harmonic motion, which in the case of a spring and a mass has an angular velocity

        w = [tex]\sqrt{k/m}[/tex]

To apply this formula to our case, let's look for the equivalent constant of the springs.

Let's start with the springs in parallels.

* the three springs in the upper part, when stretched, lengthen the same distance, therefore the total force is

       F_total = F₁ + F₂ + F₃

the springs fulfill Hooke's law and indicate that the spring constant is the same for all three,

       F_total = - k x - k x - kx = -3k x

         

therefore the equivalent constant for the combination of the springs at the top is

      k₁ = 3 k

* the two springs at the bottom

following the same reasoning the force at the bottom is

        F_total2 = - 2 k x

the equivalent constant at the bottom is

         k₂ = 2 k

now let's work the two springs are equivalent that are in series

the top spring is stretched by an amount x₁ and the bottom spring is stretched x₂

            x₂ = x -x₁

            x₂ + x₁ = x

if we consider that the springs have no masses we can use Hooke's law

            [tex]-\frac{F_{1} }{k_{1} } - \frac{F_{2}}{k_{2} } = \frac{F}{k_{eq} }[/tex]

therefore the equivalent constant is the series combination is

             [tex]\frac{1}{k_{eq} } = \frac{1}{k_{1} } + \frac{1}{k_{2} }[/tex]

we substitute the values

             \frac{1}{k_{eq} }  = \frac{1}{3k } + \frac{1}{2k }  

             \frac{1}{k_{eq} }  = \frac{5}{6k} }  

              k_eq = [tex]\frac{6k}{5}[/tex]  

therefore the angular velocity is

             w = [tex]\sqrt{\frac{6k}{5m} }[/tex]  

           

angular velocity, frequency, and period are related

           w = 2π f = 2π / T

           T = 2π / w

            T = 2π [tex]\sqrt{\frac{5m}{6k} }[/tex]

           T₀ = 2π [tex]\sqrt{\frac{m}{k} }[/tex]

           T = [tex]\sqrt{\frac{5}{6} }[/tex] T₀

Essential Questions: What does the particle theory tell us about the nature of matter? How does
each state of matter behave?

Answers

sowwie :( i need points

Explanation:

Why do dumplings cook faster in oil than water?

Answers

Answer:

oil heats faster

Explanation:

that's all

Answer:

Oil gets hotter faster or something

in 1-2 complete sentences define "opportunity cost " in your own words ​

Answers

Answer:

Here you go, hope this helps! :)

Explanation:

Opportunity cost is the value of the next best thing you give up whenever you make a decision. It is "the loss of potential gain from other alternatives when one alternative is chosen". ... For example, opportunity cost is how much leisure time we give up to work.

The area of the foundation of a square house is 840 ft. Find
the side length of the foundation of the house to nearest whole
number

Answers

Answer:

210 ft.

Explanation:

Since a square has 4 sides and all sides are equal, just do 210 divided by 4.

PLEASE HELP i’m giving 32 points!!

1.) How many grams of
potassium chloride (KCI)
can be dissolved at 80°C?

2.) At 50°C, how much potassium chlorate (KCIO3) can be dissolved in 300 grams of water?

Answers

Answer: 1 How many grams of KCl will dissolve in 1 liter of H2O at 50 °C? 5. 58.0 g of K2Cr2O7 is added to 100 g H2O at. 0 °C. With constant stirring, to what temp-.                                                                                                                                     2  34 °C? 4. How many grams of KCl will dissolve in 1 liter of H2O at 50 °C? 5. 58.0 g of ... A saturated solution of KClO3 was made with 300 g of H2O at. 34 °C.

Explanation:

first person is right :)


Energy that travels in waves through matter

Answers

A mechanical wave is a disturbance in matter that transfers energy through the matter. The matter through which a mechanical wave travels is called the medium

or media in plural.

Mechanical wave are waves that travels through a medium or matter.

What are mechanical wave?

A wave is a disturbance that travels or propagates from the place where it was created.

Waves transfer energy from one place to another, but they do not necessarily transfer any mass.

There are two types of waves;

mechanical wave and electromagnetic waves

electromagnetic waves are waves that that do not need any means of medium for propagation.

Examples of electromagnetic wave includes; light wave , radio wave e.t.c

Mechanical waves are waves that need medium for propagation. Example of mechanical waves includes ; sound wave , water wave e.t.c

learn more about mechanical wave from

https://brainly.com/question/26116832

#SPJ6

Why does liquid water boil away when exposed to the Martian atmosphere?

a. the surface of Mars is much hotter than the surface of Earth.
b. it is quickly absorbed into the dry soil.
c. radiation from the Sun passes through Mars' atmosphere and boils the water.
d. the low air pressure lowers the boiling point

Answers

Answer: d. the low air pressure lowers the boiling point

Explanation:

Note that there cannot be less than 6.1 millibars of liquid water. This fact is important because the Martian surface atmospheric pressure hovers just below that value. Any water that could form from melting water on a warm afternoon will easily vanish into the desiccated Martian atmosphere.

A 3kg plastic tank that has a volume of 0.2m ^3 Is filled with liquid water . Assuming the density of water is 1000kg/m^3 determine the weight of the combined system

Answers

Answer:

The weight of the combined system is 1989.8 N.

Explanation:

The weight, W, of an object can be expressed as;

W = mg

where m is the mass of the object, and g is the acceleration due to gravity.

Weight of the combined system = weight of tank + weight of water

mass of the plastic tank = 3 kg

weight of the plastic tank = m x g

                               = 3 x 9.8

                               = 29.4 N

Weight of the plastic tank is 29.4 N

But,

density = [tex]\frac{mass}{volume}[/tex]

mass = density x volume

volume of water = 0.2 [tex]m^{3}[/tex], density of water = 1000 kg/[tex]m^{3}[/tex].

mass  = 1000 x 0.2

         = 200

mass of water = 200 kg

weight of water = 200 x 9.8

                   = 1960 N

Thus,

combined weight of the system = 29.4 + 1960

                        = 1989.8 N

The weight of the combined system is 1989.8 N.

Other Questions
Shasta is going to her best friend's house for dinner. Her mother says she needs to be back in 2 and a half hours. If she leaves at 5:00 pm, what time will she be back? Ashkey gets $9,000 a year from the government to pay for school. Her school costs $3,000 for She is away from home for 8 months. She pays $400 a month for rent. Her phone averages $50 a monthShe pays about $150 a month in groceries. Create a budget for How much does she have left for activities for the 8 months? what is the volume of the cylinder below? Realizeaz expansiunea atributelor scrise italic n versurile de mai jos, desprind n propoziii fraza obinut i indicnd felul acestora.Glasul ei limpedei neneles se aude.Va ROG E URGENT What does anaerobic mean?A. Short bursts of energyB. Without oxygenC. Intense physical outputD. With oxygen What is the healthiest hydrator? Pls I need the answer -10 + x < -10Solve the linear inequality for x. plz help An accountant passed the closing entries of the expenses and then closed all the expense accounts by crediting them. Which account should she debit to complete the dual aspect of the journal entry How does gradualism explain the evolution of different species?New species appear as a result of small changes over a long period of time New species appear as a result of small changes over a short period of time New species appear as a result of big changes in a short period of time New species appear as a result of big changes over a short period of time Please please helpppp!!! NAME THIS SONG AND ARTIST Karma policeArrest this manHe talks in mathsHe buzzes like a fridgeHe's like a detuned radioKarma policeArrest this girlHer Hitler hairdoIs making me feel illAnd we have crashed her partyThis is what you'll getThis is what you'll getThis is what you'll getWhen you mess with usKarma policeI've given all I canIt's not enoughI've given all I canBut we're still on the payrollThis is what you'll getThis is what you'll getThis is what you'll getWhen you mess with usFor a minute thereI lost myself, I lost myselfPhew, for a minute thereI lost myself, I lost myselfFor a minute thereI lost myself, I lost myselfPhew, for a minute thereI lost myself, I lost myself In sexually reproducing organisms, such as humans, which of the following statements isTRUE about the DNA found in the cells of the children? hola gente como estan hoy why does the temp of the air increase with the height of the stratosphere? Practice using graphs of equivalent ratios. On a coordinate plane, point (2, 3) is plotted.A 2-column table with 3 rows. Column 1 is labeled x with entries 2, blank, blank. Column 2 is labeled y with entries 3, blank, blank. The table shows one point from the given graph. How could you find more ordered pairs to create a graph and table of equivalent fractions? Check all that apply. Include the point (0, 0), which is on every graph of equivalent ratios. Multiply both 2 and 3 by 4. Multiply 2 by 2 and 3 by 3. Start at the point on the grid. Move right 2 and up 3 and plot the point. Multiply 2 by 3 and 3 by 2. [Calculus] find average velocity given position of particle. Show steps, please! I need someone to write a 5 paragraph essay on African Americans in the 19th century.I need a rough draft tonight and a final draft ASAP. I will do absolutely anything for this!!! A group of friends decided to share 4 chocolate bars. If each friend only 2/3 of a chocolate bar how many friends shared the chocolate bars? PLEASE HELP!!Revise the following essay so that its more appropriate for the task, purpose, and audience describe in the prompt. Prompt:Write and argumentative essay aimed at your legislator that explains a few problems related to climate change and argues for a reasonable change that ordinary people can make to help solve these problems. Essay:One way that we can help keep climate change from getting worse is by usingpublic transportation rather than individual cars whenever possible.These changes in heat affect the entire globe's climate but not always in thesame way. One outcome of climate change is extreme weather not justextreme heat or drought, but also tornadoes, hurricanes, floods, and otherdisasters that used to happen just once in a blue moon. Climate change is theresult of carbon emissions in the atmosphere trapping heat that wouldnormally leave through the ozone.Cars are responsible for 28 percent of carbon emissions in the United States.If each person rode the bus just one day a week, carbon emissions could bereduced by almost 40 percent. In 1630 at the beginning of European settlement, about 425,000,000 hectares of the United States were covered with trees. By 2017, the area covered by trees was reduced to 300,000,000 hectares. What is the percentage decrease in the area covered by trees between 1630 and 2017?