Physics

Electromagnetic Waves and Spectrum

659 Questions

Electromagnetic waves and spectrum questions test a candidate's understanding of radiation frequencies, wavelengths, and the properties of different rays like infrared, ultraviolet, and visible light. Concepts also cover practical applications in astronomy and the fundamental speed of light calculations. This physics topic appears regularly in general science sections of major competitive examinations.

UV rays propertiesElectromagnetic radiation frequencyWavelength identificationSpeed of light calculationsBlack body radiation

Electromagnetic Waves and Spectrum Questions

Multiple choice

Which of the following statements is wrong?

  1. All photons do not carry the same amount of energy

  2. The energy of radiation increases with decrease in the wavelength

  3. The energy of radiation increases with increase in the wave number

  4. None of these

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the given statements are correct.

Multiple choice

The approximate velocity of light is

  1. 3x106 m per second

  2. 3x108 m per second

  3. 3x1010 m per second

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The speed of light in a vacuum is approximately 300,000,000 meters per second, which is written in scientific notation as 3 x 10^8 m/s.

Multiple choice

Electromagnetic radiation is emitted by

  1. X-rays

  2. Ultrasonic

  3. Electrons

  4. Protons
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electrons are responsible for emission of most Electromagnetic radiation because they have low mass, and therefore are easily accelerated by a variety of mechanisms.  

Multiple choice

Infrared radiation has the ……….. wave length.

  1. longest

  2. strongest

  3. shortest

  4. widest
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Infrared radiation has wavelengths longer than visible light but shorter than microwaves. Among the choices provided, it is characterized by its relatively long wavelength.

Multiple choice physics optoelectronic devices resistance and temperature

A laser operates at a frequency of $3\times 10^{14} H _z$ and has an aperture of $1cm$. The radii spread of the beam is 

  1. $10^{-3}$ radian
  2. $5\times 10^{-3}$ radian
  3. $10^{-4}$ radian
  4. $10^{-2}$ radian
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Due to non ideality in monochromatic nature of a laser, there exists some spread $\theta$, 


$\theta =\dfrac { \lambda  }{ \pi r } =\dfrac { c }{ \pi fr } $

$\theta={ 10 }^{ -4 } \ radian$

Multiple choice physics optoelectronic devices resistance and temperature

Wavelength of a laser beam can be used as a standard of:

  1. time

  2. temperature

  3. angle

  4. length
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Wavelength of a laser beam can be used as a standard of  length because wavelength is considered as the measure of length of the wave.