# 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

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