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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 of the following is not an example of a chemical reaction? Rust, Photosynthesis, Melting Ice, Heat from Fire?
FinnZ [79.3K]
Rust, photosynthesis, and heat from fire are all chemical reactions <span>because </span>new substances are formed and the chemical formula is changed. By doing this, bonds are broken and formed in the making of the new substance. Melting ice is physical change the molecules are still water molecules, it just changed physical form. 
5 0
3 years ago
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Why does a 10 gram piece if copper take up more space than a 10 gram piece of gold
algol [13]

Answer:

because the mass of the copper is higher than the mass of the gold.

Explanation:

7 0
3 years ago
A thick steel sheet of area 100 in.2 is exposed to air near the ocean. After a one-year period it was found to experience a weig
vladimir1956 [14]

Answer:

Therefore the rate of corrosion 37.4 mpy and 0.952 mm/yr.

Explanation:

The corrosion rate is the rate of material remove.The formula for calculating CPR or corrosion penetration rate is

CPR=\frac{KW}{DAT}

K= constant depends on the system of units used.

W= weight =485 g

D= density =7.9 g/cm³

A = exposed specimen area =100 in² =6.452 cm²

K=534 to give CPR in mpy

K=87.6  to give CPR in mm/yr

mpy

CPR=\frac{KW}{DAT}

        =\frac{534\times( 485g)\times( 10^3mg/g)}{(7.9g/cm^3) \times (100in^2)\times (24h/day)\times (365day/yr)\times 1yr}

        =37.4mpy

mm/yr

CPR=\frac{KW}{DAT}

        =\frac{87.6\times (485g)\times (10^3 mg/g)}{(7.9g/cm^3)\times (100in^2)\times(2.54cm/in)^2\times (24h/day)\times (365day/yr)\times 1yr}

       =0.952 mm/yr

Therefore the rate of corrosion 37.4 mpy and 0.952 mm/yr.

3 0
3 years ago
Do quasars reside within or without side of galaxies?
sveticcg [70]

They almost entirely reside within galaxies because quasars are a subset of blackholes with a large and fast enough accretion disk to generate a beam of interstellar material perpendicular to itself. This typically only occurs in the largest black holes at the center of galaxies (supermassive blackholes) or at least stellar black holes---which still occur within galaxies because the material is necessary to form them.

6 0
3 years ago
7. Which best describes the energy change th pushes a large rock down a hill?
svlad2 [7]

Answer:

B

Explanation:

Gravitational Energy is the energy of position or place. A rock resting at the top of a hill contains gravitational Potential energy. Hydropower, such as water in a reservoir behind a dam, is an example of gravitational potential energy.

6 0
3 years ago
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