# Electromagnetic Waves

### If a source of power 4 kW produces 10^20 photons/second

If a source of power 4 kW produces 1020 photons/second, the radiation belongs to a part of the spectrum called

1. microwaves
2. X rays
3. γ rays
4. ultraviolet rays

### An electromagnetic wave of frequency v = 3.0 MHz passes

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then

1. wave length is double and frequency becomes half
2. wave length is double and the frequency remains unchanged
3. wave length is halved and frequency remains unchanged
4. wave length and frequency both remain unchanged

### Infra red radiation is detected by

Infra red radiation is detected by

1. photometer
2. nanometer
3. spectrometer
4. pyrometer

### Arrange the following electromagnetic radiations per quantum in the order of increasing energy

Arrange the following electromagnetic radiations per quantum in the order of increasing energy:

A: Blue light; B: Yellow light; C: X-ray; D: Radio wave

1. A, B, D, C
2. C, A, B, D
3. B, A, D, C
4. D, B, A, C