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LenaWriter [7]
3 years ago
9

Dish-shaped reflectors are used to steer microwaves in order to establish communications links between nearby buildings. Those r

eflectors are often made from metal mesh. Why don't they have to be made from solid metal sheets
Physics
1 answer:
Ad libitum [116K]3 years ago
5 0

A "screen" or even just a set of parallel bars are highly reflective to electromagnetic waves as long as the open spaces are small compared to the wavelengths.

"Grid" dishes work fine ... with less weight and less wind resistance ... for frequencies below about 3 GHz. (Wavelengths of at least 10 cm.)

(I even worked on a microwave system in South America where huge grid dishes were used on a 90-mile link.)

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Which principle(s) of the cell<br> theory shows that all organisms<br> are somehow similar?
Stolb23 [73]

Explanation:

The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.

hope it helps

plz mark as brainliest

7 0
3 years ago
What happens to jetstream’s as they get closer to the equator
MAVERICK [17]

Answer:They stop because jet streams follow boundaries between hot and cold air.

Explanation:

6 0
3 years ago
Read 2 more answers
Assuming that the limits of the visible spectrum are approximately 380 and 700 nm, find the angular range of the first-order vis
ch4aika [34]

Answer:

angular range is ( 0.681 rad , 0.35 rad )

Explanation:

given data

wavelength λ = 380 nm = 380 × 10^{-9} m

wavelength λ  = 700 nm =  700 × 10^{-9} m

to find out

angular range of the first-order

solution

we will apply here slit experiment equation that is

d sinθ = m λ    ...........1

here m is 1 for single slit and d is = \frac{1}{900*10^3 m}

so put here value in equation 1 for 380 nm

we get

d sinθ = m λ

\frac{1}{900*10^3} sinθ = 1 × 380 × 10^{-9}

θ = 0.35 rad

and for 700 nm

we get

d sinθ = m λ

\frac{1}{900*10^3} sinθ = 1 × 700 × 10^{-9}

θ = 0.681 rad

so angular range is ( 0.681 rad , 0.35 rad )

3 0
3 years ago
A planet exerts a gravitational force of magnitude 4e22 N on a star. If the planet were 3 times closer to the star (that is, if
Alex_Xolod [135]

Answer:

3.6\times10^{23} N

Explanation:

F=\frac{GmM}{r^2}=4\times10^{22} N

F'=\frac{GmM}{(r/3)^2}=9\frac{GmM}{r^2}=9\times4\times10^{22}=3.6\times10^{23} N

7 0
2 years ago
5.3 two 30 kg children in a 20 kg cart are stationary at the top of a hill. They start rolling down the 80 m tall hill and they
Makovka662 [10]

Answer:

<em>60008.4 J</em>

<em></em>

Explanation:

The mass of each kid = 30 kg

mass of the cart = 20 kg

The speed of the cart down the hill = 30 km/hr = 30 x 1000/3600 = 8.33 m/s

The height of the hill = 80 m

The potential energy of the boys at the top of the hill = mgh

where

m is the total mass of the kids and the cart = (30 x 2) + 20 = 80 kg

g is the acceleration due to gravity = 9.81 m/s^2

h is their height above the ground = 80 m (on the top of the hill)

substituting, we have

potential energy PE = 80 x 9.81 x 80 = 62784 J

At an instance at the bottom of the hill

their kinetic energy = \frac{1}{2} mv^2

where

v is their velocity = 8.33 m/s

m is their total mass = 80 kg

substituting, we have

kinetic energy KE = \frac{1}{2}*80*8.33^2 = 2775.6 J

Total work done on the cart is equal to the energy lost by the cart when it reached the bottom of the hill

work done by friction = PE - KE = 62784 - 2775.6 = <em>60008.4 J</em>

5 0
3 years ago
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