The energy of the EM waves is of the order of 15 keV. To which part of the spectrum does it belong?
1. X-rays
2. Infrared rays
3. Ultraviolet rays
4. γ-rays
Light with an energy flux of 25×104 Wm–2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm2, the average force exerted on the surface is:
1. 1.25×10−6 N
2. 2.50×10−6 N
3. 1.20×10−6 N
4. 3.0×10−6 N
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is:
1. | the frequency of microwaves has no relation with the natural frequency of water molecules. |
2. | microwaves are heatwaves, so always produce heating. |
3. | infrared waves produce heating in a microwave oven. |
4. | the frequency of the microwaves must match the resonant frequency of the water molecules. |
1. | wavelength is doubled and frequency becomes half |
2. | wavelength is halved and frequency remains unchanged |
3. | wavelength and frequency both remain unchanged |
4. | wavelength is doubled and frequency unchanged |
The ratio of the amplitude of a magnetic field to the amplitude of an electric field for an electromagnetic wave propagating in a vacuum is equal to:
1. | reciprocal of speed of light in vacuum. |
2. | the ratio of magnetic permeability to the electric susceptibility of vacuum. |
3. | unity. |
4. | the speed of light in a vacuum. |
The electric and the magnetic fields, associated with an electromagnetic wave, propagating along the positive Z-axis, can be represented by:
1. [E=E0ˆk, B=B0ˆi]
2. [E=E0ˆj, B=B0ˆj]
3. [E=E0ˆj, B=B0ˆk]
4. [E=E0ˆi, B=B0ˆj]
1. | gamma rays, ultraviolet, infrared, microwaves. |
2. | microwaves, gamma rays, infrared, ultraviolet. |
3. | infrared, microwave, ultraviolet, gamma rays. |
4. | microwave, infrared, ultraviolet, gamma rays. |
Which of the following statement is false for the properties of electromagnetic waves?
1. | Both electric and magnetic field vectors attain the maxima and minima at the same place and same time. |
2. | The energy in the electromagnetic wave is divided equally between electric and magnetic vectors. |
3. | Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of the wave. |
4. | These waves do not require any material medium for propagation. |