Light Class 8 Numericals – solved numerical questions

Last updated on July 4th, 2023 at 02:07 pm

In this post, we will solve Numerical problems based on the Light chapter of class 8 science. Here, first, we will go through the law of reflection & related formulas, and then attempt the numerical questions. Solution & answer is given for all the numerical questions.

Formulas Used

1 ] According to the law of reflection,
Angle of incidence <i = Angle of reflection <r

2] Angle of incidence = angle between the normal and incident ray

3] Angle of reflection = angle between the normal and reflected ray

4] Angle between Normal and plane mirror = 90⁰

Light Class 8 Numericals – Questions and Answers

1. If the reflected ray makes an angle of 600 with the normal, what angle must the incident ray make with the normal?

Solution:

Given:

The angle of reflection = <r = 60⁰.
The angle of incidence = <i =?

According to the law of reflection, <i = <r
But r = 60⁰
Hence, <i= 60⁰
The incident ray will make an angle of 60⁰ with the normal.

2. If the angle between the incident ray and the reflected ray is 90⁰, what are the values of the angle of incidence and angle of reflection?

Solution:

Given: The angle between the incident ray and the reflected ray is 90⁰.
i.e. <i + <r = 90⁰ ………….(1)
According to the law of reflection,
<i = <r ………….(2)

<i + <i = 90⁰
=>2 <i = 90⁰
So, <i= 45⁰
The angle of incidence is 45⁰ and hence, the angle of reflection is also 45⁰.

3. The angle between the plane mirror and incident ray is 35⁰, what is the angle of incidence and angle of reflection?

Solution:

To solve this numerical the above figure will be helpful.

The angle between the plane mirror and the incident ray is 35⁰
So, the angle between the normal and incident ray is = 90⁰– 35⁰ = 55⁰
This is actually the angle of incidence.
According to the law of reflection, the angle of reflection = angle of incidence = 55⁰
Answer: angle of reflection = angle of incidence = 55⁰

4. What angle will the reflected ray make with the mirror if the angle of incidence is 40⁰?

Solution:

The angle of incidence = 40⁰
So, the angle of reflection = 40⁰
The angle of reflection = angle between the reflected ray and the normal = 40⁰
So, the angle between the reflected ray and the mirror = 90⁰ – 40⁰ = 50⁰