Electromagnetic Waves

Previous Years' CBSE Board Questions

8.2 Displacement Current

MCQ

Displacement current exists only when

1. electric field is changing.
2. magnetic field is changing.
3. electric field is not changing.
4. magnetic field is not changing. (2020)

VSA (1 mark)

How is displacement current produced between the plates of a parallel plate capacitor during charging?

(2020)

1. The charging current for a capacitor is 0.25 A. What is the displacement current across its plates?

(Foreign 2016) (AP)

SAI (2 marks)

1. What is a displacement current? How is it different from a conduction current?

(2023) U

1. A parallel plate capacitor of plate area A each and separation d, is being charged by an AC source. Show that the displacement current inside the capacitor is the same as the current charging the capacitor.

(Al 2019) 🕡

OR

1. How does Ampere-Maxwell law explain the flow of current through a capacitor when it is being charged by a battery? Write the expression for the displacement current in terms of the rate of change of electric flux. (Delhi 2017) (An)

describe briefly how the concept of displacement

current is explained through charging/discharging of

a capacitor in an electric circuit.

(Al 2015) Cr

8.3 Electromagnetic Waves

MCQ

The oscillating electric and magnetic field vectors in

an electromagnetic wave are

1. perpendicular to each other and opposite in phase.
2. parallel to each other and opposite in phase.
3. perpendicular to each other and in the same phase.
4. parallel to each other and in the same phase.

(2020C)

VSA (1 mark)

11. What oscillates in an electromagnetic wave of

frequency 10 MHz? (2021C)

Depict the field diagram of an electromagnetic wave

propagating along positive X-axis with its electric

field along Y-axis. (2020) U

1. Illustrate by giving suitable examples, how you can show that electromagnetic waves carry both energy and momentum. (Al 2019)
2. How is the speed of em waves in vacuum determined by the electric and magnetic fields? (Delhi 2017) (R

Write the relation for the speed of electromagnetic

waves in terms of the amplitudes of electric and

magnetic fields. (AI 2017)

1. Write the relations (i) between the speed of light and the amplitudes of electric and magnetic fields,
2. for the speed of em wave in terms of a permittivity <math>\varepsilon_0</math>, and magnetic permeability, <math>\mu_0</math>, of the medium.

next to infrared radiations in the electromagnetic

spectrum on

1. (b) longer wavelength side. (2020C)

(2019C)

1. What do you understand by the statement, "Electro-magnetic waves transport momentum"? (1/2, 2018)

SA II (3 marks)

Write the expression for the speed of light in a material medium of relative permittivity <math>\varepsilon_r</math> and relative magnetic permeability μ_r. (1/3, 2020)

1. Prove that the average energy density of the oscillating electric field is equal to that of the oscillating magnetic field. (2/3, Delhi 2019) U
2. How are e.m. waves produced by oscillating charges? Draw a sketch of linearly polarized e.m. waves propagating in the z-direction. Indicate the directions of the oscillating electric and magnetic fields. (Delhi 2016) [EV]

8.4 Electromagnetic Spectrum

MCO

1. Name the electromagnetic waves also known as 'heat waves'.
2. Radiowaves (b) Microwaves
3. X-rays (d) Infrared waves

(2023) An

(2023)

1. Which one of the following electromagnetic radiation has the least wavelength?
2. Gamma rays (b) Microwaves
3. Gamma rays (b) Microwaves
4. Visible light (d) X-rays (2023) R

(2020) An

1. A welder wears special glasses to protect his eyes mostly from the harmful effect of
2. very intense visible light
3. infrared radiation
4. ultraviolet rays
5. microwaves. (2020) (R)

Electromagnetic waves used as a diagnostic tool in medicine are

1. X-rays (b) ultraviolet rays
2. infrared radiation (d) ultrasonic waves.

1. Which part of the electromagnetic spectrum is used in RADAR? Give its frequency range. (2019)
2. Name the part of the electromagnetic spectrum which has the longest wavelength and write its one use. (2019C)

The small ozone layer on top of the stratosphere is

crucial for human survival. Why? (Al 2019) [U

Name the electromagnetic radiations used for

(a) water purification, and (b) eye surgery. (2018)

1. Why are microwaves considered suitable for radar systems used in aircraft navigation? (Delhi 2016)
2. To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong? (Al 2014) (R

36. Arrange the following electromagnetic waves in

order of increasing frequency.

y-rays, Microwaves, Infrared rays and Ultraviolet

rays. (Foreign 2014) (Ap)

SAI (2 marks)

Write any two characteristics of an electromagnetic

wave. Why are microwaves used in radar systems?

Which of the following electromagnetic waves has (a)

minimum wavelength, and (b) minimum frequency?

Write one use of each of these two waves.

Infrared waves, Microwaves, γ-rays and X-rays

(2020)

(2020)

Gamma rays and radio waves travel with the same

velocity in free space. Distinguish between them in

terms of their origin and the main application.

Why are infrared waves often called heat waves?

Explain. (1/2, 2018)

Identify the electromagnetic waves whose wavelengths

vary as (a) 10^-12 m < λ < 10^-8 m

(b) 10^-3 m < λ < 10^-1 m

Write one use for each. (Al 2017)

(2020) R

Identify the electromagnetic waves whose