Class 10 Physics Chapter 5
Important Questions

The electromagnetic (EM) spectrum is a fundamental concept in physics, and it describes the entire range of electromagnetic waves in order of their frequency or wavelength. Electromagnetic waves are oscillating electric and magnetic fields that move through space, and they all travel at the speed of light in a vacuum. Here you will find class 10 spectrum important questions and answers.


The electromagnetic (EM) spectrum encompasses the entirety of electromagnetic waves, characterised by their differing frequencies or wavelengths. This spectrum illustrates the vast range of electromagnetic radiation, from long radio waves used in communication, to the visible light that we perceive, and even to the high-energy gamma rays emitted from nuclear reactions. If you want to prepare well then below are some spectrum class 10 ICSE questions.

What is the Spectrum?

The term “spectrum” encompasses a diverse array of contexts, each portraying a continuum or range of elements within its domain. From the expansive electromagnetic spectrum encompassing gamma rays to radio waves, to the visible light spectrum spanning the rainbow of colors discernible by the human eye, the term navigates realms of physics and perception. If you want to practice more questions and clear your understanding, then oswal.io provides you with ICSE class 10 physics spectrum questions and answers.
important questions for class 10 icse physics

Class 10 Spectrum Important Questions and Answers

Q1.The extreme colours in pure spectrum of light are ................ .
(a) violet and red
(b) violet and green
(c) green and red
(d) black and white.

Ans. (a) violet and red

The extreme colors in a pure spectrum of light (as seen in a rainbow or produced by the dispersion of white light through a prism) are:

  • Red at one end (with the longest wavelength).
  • Violet at the other end (with the shortest wavelength).

So, the extreme colors in a pure spectrum of light are red and violet

Q2. Which colour of sky would have appeared when there is no atmosphere?
(a) Blue
(b) Red
(c) No colour
(d) Black

Ans. (b) One plane, One convex

If earth doesn’t have an atmosphere, there will be scattering of light, which will make the sky appear to black. If there were no atmosphere on Earth, there would be no scattering of sunlight in the atmosphere. As a result, the sky would appear black during the day, much like how space looks to astronauts on the Moon or when they are in orbit outside of Earth's atmosphere. The Sun would appear as a bright point of light against the black background, and stars would be visible even during the day.

Q3. Which characteristic property of light is responsible for the blue colour of the sky?

The blue color of the sky is primarily due to the Rayleigh scattering of sunlight by the molecules and tiny particles in the Earth's atmosphere. Rayleigh scattering is a characteristic property of light that describes how the scattering of light is inversely proportional to the fourth power of its wavelength.
Because blue light has a shorter wavelength compared to other colors in the visible spectrum, it is scattered more by the molecules in the atmosphere. This means blue light is scattered in all directions by the gases and particles in the sky, making the sky predominantly blue during a clear day.

Q4. A prism causes dispersion of white light while a rectangular glass block does not. Explain.

In a prism, the refraction of light takes place at the two slant surfaces. The dispersion of white light occurs at the first surface of prism where its constituent colours are deviated through different angles. At the second surface, these splitted colours suffer only refraction and they get further separated. But in a rectangular glass block, the refraction of light takes place at the two parallel surfaces. At the first surface, although the white light splits into its constituent colours on refraction, but these splitted colours on suffering from refraction at the second surface emerge out in the form of a parallel beam, which give an impression of white light.

Q5. Name two sources of ultraviolet radiations?

Sun, and Artificial lamps and bulbs are two sources of ultraviolet radiations.
The Sun: The Sun is the primary natural source of UV radiation. Solar radiation includes UV-A, UV-B, and UV-C rays. However, most of the UV-C rays and a portion of UV-B rays are absorbed by the Earth's atmosphere, primarily by the ozone layer.
Artificial Lamps and Bulbs: There are several artificial sources of UV radiation, including black lights, mercury-vapor lamps, tanning lamps, and UV sterilization lamps (used to disinfect air, water, and surfaces). Some types of lasers can also produce UV radiation.

ICSE Class 10 Physics Chapter wise Important Questions


Many natural phenomena, like the blue sky or the red sunsets, can be explained by understanding the scattering and absorption of different parts of the electromagnetic spectrum. For those looking for extra practice and a better grasp of the chapter’s concepts, oswal.io provides a wide range of spectrum class 10 ICSE questions and answers, allowing for a more in-depth comprehension of the subject matter.

Frequently Asked Questions

Ans: The electromagnetic spectrum is a continuous range of all electromagnetic waves arranged by frequency or wavelength. It includes everything from radio waves used in communication to the visible light we see to the gamma rays emitted from nuclear reactions.
Ans: The electromagnetic spectrum is organized from waves with the longest wavelengths (and lowest frequencies) to waves with the shortest wavelengths (and highest frequencies). The main regions, in order, are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Ans: Human eyes are sensitive only to a small portion of the electromagnetic spectrum, known as visible light. Other parts of the spectrum have wavelengths either too long or too short for our eyes to detect.
Ans: Yes. High-energy electromagnetic waves, such as X-rays and gamma rays, carry enough energy to ionise atoms and can be harmful to living tissues. Ultraviolet (UV) rays can also be harmful and cause sunburns or increase the risk of skin cancer
Ans: Dispersion occurs when different wavelengths (or colours) of light travel at slightly different speeds in a medium. This causes them to bend by different amounts, separating them into their constituent colours. A common example is white light dispersing into a spectrum of colours when it passes through a prism.