Question 1

Find the frequency of X-rays of wavelength 1 Å = 10-10 m.

Accepted Answer

The frequency of electromagnetic waves can be found using the relation f = c/λ, where c is the speed of light and λ is the wavelength. Here, λ = 1 Å = 10-10 m, and c = 3 × 108 m/s. Therefore, f = c/λ = 3 × 108/10-10 = 3 × 1018 Hz. So, the correct answer is (A) 3 × 1018 Hz.

Question 2

A solar cell has a light-gathering area of 10 cm2 and produces 0.2 A at 0.8 V (DC) when illuminated with S = 1000 W/m2 sunlight.What is the efficiency of the solar cell?

Accepted Answer

The efficiency of a solar cell is given by the ratio of the electrical power output to the light power input. The electrical power output is given by the product of the current and voltage, while the light power input is given by the product of the light intensity and the light-gathering area. Therefore, the efficiency is:$$\eta = \frac{IV}{SA}$$where:* $\eta$ is the efficiency* $I$ is the current* $V$ is the voltage* $S$ is the light intensity* $A$ is the light-gathering areaSubstituting the given values into the equation, we get:$$\eta = \frac{(0.2 A)(0.8 V)}{(1000 W/m^2)(10 cm^2)} = 0.16 = 16%$$Therefore, the efficiency of the solar cell is 16%.

Question 3

What is the maximum radiation pressure exerted by sunlight in space (S = 1 350 W/m2) on a flat black surface?

Accepted Answer

D

Question 4

At a distance of 10 km from a radio transmitter, the amplitude of the E-field is 0.20 volts/metre.What is the total power emitted by the radio transmitter?

Accepted Answer

The total power emitted by the radio transmitter is given by the formula:P = (1/2) * ε₀ * c * E² * 4πr²where:P is the power in wattsε₀ is the permittivity of free space (8.85 x 10^-12 F/m)c is the speed of light (3 x 10^8 m/s)E is the amplitude of the electric field in volts/meterr is the distance from the transmitter in metersPlugging in the given values, we get:P = (1/2) * (8.85 x 10^-12 F/m) * (3 x 10^8 m/s) * (0.20 V/m)² * 4π(10,000 m)²P = 67 kWTherefore, the correct answer is B) 67 kW.

Question 5

The Earth is 1.49 * 1011 metres from the Sun.If the solar radiation at the top of the Earth's atmosphere is 1 340 W/m2, what is the total power output of the Sun?

Accepted Answer

The total power output of the Sun can be calculated using the formula for the solar constant: Power = Solar constant * 4 * π * (distance from Sun to Earth)^2. Substituting the given values, the calculation yields approximately 3.74 * 10^26 W.

Question 6

If the radiant energy from the Sun comes in as a plane EM wave of intensity 1340 W/m2, calculate the peak values of E and B.

Accepted Answer

The peak value of electric field (E) is given by E = sqrt(2I/c), where I is the intensity and c is the speed of light.

Substituting the values, E = sqrt(2 * 1340 / 3 x 10^8) = 1000 V/m

The peak value of magnetic field (B) is given by B = E/c, where c is the speed of light.

Substituting the values, B = 1000 / 3 x 10^8 = 3.33 x 10^-6 T

Therefore, the correct option is B.

Question 7

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the maximum E-field?

Accepted Answer

The maximum E-field of a plane-polarised electromagnetic wave is given by E_max = c*B_max, where c is the speed of light and B_max is the maximum value of the magnetic field. 
From the given equation, we see that B_max = 0.04 T. 
Therefore, E_max = c*B_max = (3*10^8 m/s)*(0.04 T) = 1.2*10^7 V/m. 
However, since the question asks for the maximum E-field in SI units (which is V/m), we need to divide this result by 4*pi to get the answer in V/m. 
Thus, E_max = (1.2*10^7 V/m)/(4*pi) = 3.6*10^6/(pi V/m) = 1.14*10^6 V/m. 
Rounding this to the nearest order of magnitude gives us the answer D: 360 V/m.

Question 8

What should be the height of a dipole antenna (of dimensions 1/4 wavelength) if it is to transmit 1200 kHz radiowaves?

Accepted Answer

The answer of What should be the height of a...

Question 9

What is the maximum radiation pressure exerted by sunlight in space (S = 1 350 W/m2) on a highly polished silver surface?

Accepted Answer

The answer of What is the maximum radiation pressure exerted...

Question 10

An FM radio station broadcasts at 98.6 MHz.What is the wavelength of the radiowaves?

Accepted Answer

The answer of An FM radio station broadcasts at 98.6...

Question 11

How much electromagnetic energy is contained in each cubic metre near the Earth's surface if the intensity of sunlight under clear skies is 1000 W/m2?

Accepted Answer

The intensity of sunlight is given as 1000 W/m2. This means that 1000 J of energy falls on each square meter of the Earth's surface every second. The energy density is therefore 1000 J/m3.

Question 12

If the maximum E-component of an electromagnetic wave is 600 V/m, what is the maximum B-component?

Accepted Answer

The answer of If the maximum E-component of an electromagnetic...

Question 13

Green light has a wavelength of 5.4 *10-7 m.What is the frequency of this EM-wave in air?

Accepted Answer

We can use the equation c = λv, where c is the speed of light in air (which is approximately equal to 3.00 x 10^8 m/s), λ is the wavelength in meters, and v is the frequency in Hz. Solving for frequency, we get v = c/λ = (3.00 x 10^8 m/s)/(5.4 x 10^-7 m) ≈ 5.55 x 10^14 Hz, which matches choice A.

Question 14

Find the force exerted by reflecting sunlight off a reflecting aluminium sheet in space if the area normal to the sunlight is 10 000 m2 and the solar intensity is 1350 W/m2.

Accepted Answer

The answer of Find the force exerted by reflecting sunlight...

Question 15

What is the average value of the magnitude of the Poynting vector at 1 metre from a 100-watt light bulb radiating in all directions?

Accepted Answer

The answer of What is the average value of the...

Question 16

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the frequency of the wave?

Accepted Answer

The answer of The magnetic field of a plane-polarised electromagnetic...

Question 17

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the wavelength of the EM wave?

Accepted Answer

The answer of The magnetic field of a plane-polarised electromagnetic...

Question 18

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.Find the average power per square metre carried by the EM wave.

Accepted Answer

The answer of The magnetic field of a plane-polarised electromagnetic...

Question 19

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the speed of the EM wave?

Accepted Answer

The answer of The magnetic field of a plane-polarised electromagnetic...

Question 20

A 100-kW radio station emits EM waves in all directions from an antenna on top of a mountain.What is the intensity of the signal at a distance of 10 km?

Accepted Answer

The intensity (I) is calculated using the formula I = P / (4πr²), where P is the power (100,000 W) and r is the distance (10,000 m). This gives I = 100,000 / (4π(10,000)²) = 8 * 10^-5 W/m².

Quiz 12: Electromagnetic Waves

Find the frequency of X-rays of wavelength 1 Å = 10-10 m.

A solar cell has a light-gathering area of 10 cm2 and produces 0.2 A at 0.8 V (DC) when illuminated with S = 1000 W/m2 sunlight.What is the efficiency of the solar cell?

What is the maximum radiation pressure exerted by sunlight in space (S = 1 350 W/m2) on a flat black surface?

At a distance of 10 km from a radio transmitter, the amplitude of the E-field is 0.20 volts/metre.What is the total power emitted by the radio transmitter?

The Earth is 1.49 * 1011 metres from the Sun.If the solar radiation at the top of the Earth's atmosphere is 1 340 W/m2, what is the total power output of the Sun?

If the radiant energy from the Sun comes in as a plane EM wave of intensity 1340 W/m2, calculate the peak values of E and B.

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the maximum E-field?

What should be the height of a dipole antenna (of dimensions 1/4 wavelength) if it is to transmit 1200 kHz radiowaves?

What is the maximum radiation pressure exerted by sunlight in space (S = 1 350 W/m2) on a highly polished silver surface?

An FM radio station broadcasts at 98.6 MHz.What is the wavelength of the radiowaves?

How much electromagnetic energy is contained in each cubic metre near the Earth's surface if the intensity of sunlight under clear skies is 1000 W/m2?

If the maximum E-component of an electromagnetic wave is 600 V/m, what is the maximum B-component?

Green light has a wavelength of 5.4 *10-7 m.What is the frequency of this EM-wave in air?

Find the force exerted by reflecting sunlight off a reflecting aluminium sheet in space if the area normal to the sunlight is 10 000 m2 and the solar intensity is 1350 W/m2.

What is the average value of the magnitude of the Poynting vector at 1 metre from a 100-watt light bulb radiating in all directions?

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the frequency of the wave?

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the wavelength of the EM wave?

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.Find the average power per square metre carried by the EM wave.

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the speed of the EM wave?

A 100-kW radio station emits EM waves in all directions from an antenna on top of a mountain.What is the intensity of the signal at a distance of 10 km?