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 <r2] 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 = 90

^{0}

**Light Class 8 Numerical 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 = 60^{0}.

The angle of incidence = <i =?

According to the law of reflection, <i = <r

But r = 60^{0}

Hence, <i= 60^{0}

The incident ray will make an angle of 60^{0} with the normal.

2. If the angle between the incident ray and the reflected ray is 90^{0}, what are the values of the angle of incidence and angle of reflection?

**Solution:**

**Given: **Angle between the incident ray and the reflected ray is 90^{0}.

i.e. <i + <r = 90^{0} ………….(1)

According to the law of reflection,

<i = <r ………….(2)

<i + <i = 90

^{0}

=>2 <i = 90^{0}

So, <i= 45^{0}

The angle of incidence is 45^{0}and hence, the angle of reflection is also 45^{0}.

3. The angle between the plane mirror and incident ray is 35^{0}, 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 35^{0}

So,^{ }the angle between the normal and incident ray is = 90^{0}– 35^{0} = 55^{0}

This is actually the angle of incidence.

According to the law of reflection, the angle of reflection = angle of incidence = 55^{0}

Answer: angle of reflection = angle of incidence = 55^{0}

4.What angle will the reflected ray make with the mirror if the angle of incidence is 40^{0}?

**Solution:**

The angle of incidence = 40^{0}

So, the angle of reflection = 40^{0}

The angle of reflection = angle between the reflected ray and the normal = 40^{0}

So, the angle between the reflected ray and the mirror = 90^{0} – 40^{0} = 50^{0}