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 physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Consider the following processes
(i) Electrical oscillation
(ii) Rapid deceleration of fast electrons
(iii) Atomic transition
Which of these are likely to produce visible light?

  1. (iii) only

  2. (ii) and (iii)

  3. (i) and (iii)

  4. (i), (ii) and (iii)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Visible light means i.e visible to human eye.

It runs about $700-400㎚$
So Basically all of these options
  1. Electrical oscillation
  2. Rapid deceleration of fast electrons
  3. Atomic transition
This is basically theoretical question.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Which one of following have highest frequency?

  1. radio waves.

  2. infrared.

  3. ultraviolet.

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

Frequency of Radio waves = $<3\times { 10 }^{ 9 }$Hz

Frequency of infrared waves = $3\times { 10 }^{ 9 }-3\times { 10 }^{ 11 }$Hz
Frequency of ultraviolet waves = $7.5\times { 10 }^{ 14 }-3\times { 10 }^{ 17 }$Hz
Frequency of gamma rays = $>3\times { 10 }^{ 20 }$Hz

So Gamma rays have highest frequency.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

The wavelength of $X$-rays is in the range

  1. $0.001\mathring { A } $ to $1\mathring { A } $
  2. $0.001 nm$ to $1 nm$
  3. $0.001 \mu m$ to $1 \mu m$
  4. $0.001 cm $ to $1 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$X$-Rays Wavelength range $=1\times { 10 }^{ -11 }m$ to $3\times { 10 }^{ -8 }m$
So,                          $=0.001 nm$ to $1 nm$

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Study the frequency of the following electromagnetic radiations and select the correct relationship.
$1$. Infra red
$2$. Microwave
$3$. Ultra violet.

  1. $3 > 2 > 1$
  2. $3 > 1 > 2$
  3. $1 > 2 > 3$
  4. $2 > 3 > 1$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electromagnetic radiation frequency increases in the order: Microwave < Infrared < Ultraviolet. Therefore, Ultraviolet (3) > Infrared (1) > Microwave (2).

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

If a source of power $4$ kW produces $10^{26}$ photons/second, the radiation belongs to a part of the spectrum called:

  1. X-rays

  2. Ultraviolet rays

  3. Microwaves
  4. $\gamma$-rays
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$4000 \ J$ of energy is produced from $10^{26}$ photons in one second.
Energy of each photon   $E = \dfrac{4000}{10^{26}} = 4\times 10^{-23} \ J$
Frequency of each photon   $\nu = \dfrac{E}{h} = \dfrac{4\times 10^{-23}}{6.63\times 10^{-34}} = 6\times 10^{10} \ Hz$
So the radiation belongs to micro waves.
Correct answer is option C.
Multiple choice

Which of the following is NOT a type of electromagnetic radiation?

  1. X-rays

  2. Gamma rays

  3. Ultraviolet rays

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

Sound waves are not a type of electromagnetic radiation. They are mechanical waves that require a medium for propagation.

Multiple choice

What is the speed of light in a vacuum?

  1. 299,792,458 meters per second

  2. 300,000,000 meters per second

  3. 340 meters per second

  4. 186,282 miles per second
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The speed of light in a vacuum is a fundamental constant in physics and is denoted by the letter c. It is equal to 299,792,458 meters per second.

Multiple choice

Which of these is a type of electromagnetic radiation with the longest wavelength?

  1. Gamma rays

  2. X-rays

  3. Ultraviolet rays

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

Radio waves have the longest wavelength among the given options.

Multiple choice

Which of the following is NOT a type of electromagnetic radiation?

  1. X-rays

  2. Gamma rays

  3. Ultraviolet rays

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

Sound waves are mechanical waves, not electromagnetic waves.

Multiple choice

Which of the following is not a type of electromagnetic radiation?

  1. Gamma rays

  2. X-rays

  3. Ultraviolet rays

  4. Infrared rays

  5. Sound waves
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Sound waves are mechanical waves that require a medium to propagate. Electromagnetic radiation, on the other hand, can travel through a vacuum.

Multiple choice

A circuit consists of a resistor of resistance (R), an inductor of inductance (L), and a capacitor of capacitance (C). The charge on the capacitor is given by the function (q(t) = Q_0\cos\omega t), where (Q_0) is the initial charge on the capacitor and (\omega) is the angular frequency of the circuit. What is the equation of motion for the charge on the capacitor?

  1. \(LC\frac{d^2q}{dt^2} + RC\frac{dq}{dt} + \frac{1}{C}q = 0\)
  2. \(LC\frac{d^2q}{dt^2} - RC\frac{dq}{dt} + \frac{1}{C}q = 0\)
  3. \(LC\frac{d^2q}{dt^2} + RC\frac{dq}{dt} - \frac{1}{C}q = 0\)
  4. \(LC\frac{d^2q}{dt^2} - RC\frac{dq}{dt} - \frac{1}{C}q = 0\)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The equation of motion for the charge on the capacitor in an LRC circuit is given by (LC\frac{d^2q}{dt^2} + RC\frac{dq}{dt} + \frac{1}{C}q = 0). This equation is a second-order linear differential equation.

Multiple choice

Which of the following is a type of electromagnetic radiation with the longest wavelength?

  1. Gamma rays

  2. X-rays

  3. Ultraviolet rays

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

Radio waves are a type of electromagnetic radiation with the longest wavelength, ranging from a few millimeters to thousands of kilometers.