Learn Science Light , Class 8 Science Light Exercise, Free Online Light Lessons

Class 8 Science Study Material

An Educational platform for Preparation and Practice Class 8. Kidsfront provide unique pattern of learning Science with free online comprehensive study material in the form of QUESTION & ANSWER for each Chapter of Science for Class 8. This study material help Class 8, Science students in learning every aspect of Light . Students can understand Light concept easily and consolidate their learning by doing Online Practice Tests on Science,Light chapter repeatedly till they excel in Class 8, Light . Free ONLINE PRACTICE TESTS on Class 8, Light comprise of Hundreds of Questions on Light , prepared by the highly professionals team. Every repeat test of Light will have new set of questions and help students to prepare themselves for exams by doing unlimited Online Test exercise on Light . Attempt ONLINE TEST on Class 8,Science,Light in Academics section after completing this Light Question Answer Exercise.

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Topic wise:Light preparation in the form of QUESTION & ANSWER.
Evaluate preparation by doing ONLINE TEST of Class 8, Science,Light .
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Light

A boy is running towards a plane mirror with speed 20 ms-1. As seen by the boy, the image moves with the speed of

a) 20 ms-1 towards him.
b) 40 ms-1 towards him.
c) 60 ms-1 towards him.
d) 80 ms-1 towards him.

✔Answer

✔Solution

Correct Answer Is : 40 ms-1 towards him.

Solution Is : The image will run towards the mirror with same speed of the boy. But as seen by the boy, it will move with the speed of (20+20) ms-1 or 40 ms-1.

When a ray of light is incident normally on a rigid opaque surface, the angle of reflection is

a) 0o.
b) 30o.
c) 60o.
d) 90o.

✔Answer

✔Solution

Correct Answer Is : 0o.

Solution Is : When a ray of light is incident normally on a rigid surface, it coincides with the normal at the point of incidence. Therefore, the angle of incidence, i.e., the angle between the incident ray and the normal is 0o. According to the Laws of Reflection, the angle of incidence is always equal to the angle of reflection. Hence, the angle of reflection is also 0o.

When a ray of light is incident normally on a rigid opaque surface, the angle of incidence is

a) 0o.
b) 30o.
c) 60o.
d) 90o.

✔Answer

✔Solution

Correct Answer Is : 0o.

Solution Is : When a ray of light is incident normally on a rigid surface, it coincides with the normal at the point of incidence. Therefore, the angle of incidence, i.e., the angle between the incident ray and the normal is 0o.

The angle between an incident ray and its reflected ray is 90o. The angle of reflection is

a) 30o.
b) 45o.
c) 90o.
d) 180o.

✔Answer

✔Solution

Correct Answer Is : 45o.

Solution Is : Angle between an incident ray and its reflected ray = Angle of incidence + Angle of reflection. Or, 90o = 2 × Angle of reflection (Since Angle of incidence = Angle of reflection) Or, Angle of reflection = 90o/2 = 45o.

An incident ray makes 30o with the normal at the point of incidence. The reflected ray will make

a) 30o with the normal.
b) 60o with the normal.
c) 90o with the normal.
d) 180o with the normal.

✔Answer

✔Solution

Correct Answer Is : 180o with the normal.

Solution Is : According to the Laws of Reflection, the angle of incidence is always equal to the angle of reflection. Therefore, the angle of reflection should also be 30o if the angle of incidence is 30o.

A reflected ray always makes an angle

a) Of 90o with the normal.
b) Of any degree with the normal.
c) Of 90o with the incident ray.
d) Equal to the angle of incidence with the normal.

✔Answer

✔Solution

Correct Answer Is : Equal to the angle of incidence with the normal.

Solution Is : According to the Laws of Reflection, angle of incidence is always equal to the angle of reflection.

To prove experimentally, that white light consists of seven colours, we use a

a) Square card board cloured with seven colours of rainbow.
b) Black coloured card board.
c) Cirular disc cloured with seven colours of rainbow.
d) Rectangular card cloured with seven colours of rainbow.

✔Answer

✔Solution

Correct Answer Is : Square card board cloured with seven colours of rainbow.

Solution Is : Sir Isaac Newton demonstrated that white light is a combination of the seven different colours found in a rainbow (splitting of white sunlight through the prism into seven colours). If a small circular disc, with seven rainbow colours painted on it, is rotated fast, the colours fade into white colour.

The wavelength of visible light is in the range

a) 4 × 10-7 m to 8 × 10-7 m.
b) 4 × 107 m to 8 × 107 m.
c) 4 × 103 m to 8 × 103 m.
d) 4 × 104 m to 8 × 104 m.

✔Answer

✔Solution

Correct Answer Is : 4 × 10-7 m to 8 × 10-7 m.

Solution Is : Wavelength of visible region of light is 4 x 10?7 m to 8 x 10?7 m.

The image that can be obtained on a screen is

a) Real.
b) Virtual.
c) Upright.
d) Inverted.

✔Answer

✔Solution

Correct Answer Is : Real.

Solution Is : Real images are those where light actually converges, whereas virtual images are locations from where light appears to diverge.

According to the laws of reflection

a) Angle i = Angle r
b) Sine i = sine r
c) Sine i / Sine r = constant
d) Tani= tan r

✔Answer

✔Solution

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Class 8 Science Study Material

Light

A boy is running towards a plane mirror with speed 20 ms-1. As seen by the boy, the image moves with the speed of

Correct Answer Is : 40 ms-1 towards him.

Solution Is : The image will run towards the mirror with same speed of the boy. But as seen by the boy, it will move with the speed of (20+20) ms-1 or 40 ms-1.

When a ray of light is incident normally on a rigid opaque surface, the angle of reflection is

Correct Answer Is : 0o.

When a ray of light is incident normally on a rigid opaque surface, the angle of incidence is

Correct Answer Is : 0o.

Solution Is : When a ray of light is incident normally on a rigid surface, it coincides with the normal at the point of incidence. Therefore, the angle of incidence, i.e., the angle between the incident ray and the normal is 0o.

The angle between an incident ray and its reflected ray is 90o. The angle of reflection is

Correct Answer Is : 45o.

Solution Is : Angle between an incident ray and its reflected ray = Angle of incidence + Angle of reflection. Or, 90o = 2 × Angle of reflection (Since Angle of incidence = Angle of reflection) Or, Angle of reflection = 90o/2 = 45o.

An incident ray makes 30o with the normal at the point of incidence. The reflected ray will make

Correct Answer Is : 180o with the normal.

Solution Is : According to the Laws of Reflection, the angle of incidence is always equal to the angle of reflection. Therefore, the angle of reflection should also be 30o if the angle of incidence is 30o.

A reflected ray always makes an angle

Correct Answer Is : Equal to the angle of incidence with the normal.

Solution Is : According to the Laws of Reflection, angle of incidence is always equal to the angle of reflection.

To prove experimentally, that white light consists of seven colours, we use a

Correct Answer Is : Square card board cloured with seven colours of rainbow.

The wavelength of visible light is in the range

Correct Answer Is : 4 × 10-7 m to 8 × 10-7 m.

Solution Is : Wavelength of visible region of light is 4 x 10?7 m to 8 x 10?7 m.

The image that can be obtained on a screen is

Correct Answer Is : Real.

Solution Is : Real images are those where light actually converges, whereas virtual images are locations from where light appears to diverge.

According to the laws of reflection

Correct Answer Is : Angle i = Angle r

Solution Is : Angle of incidence is equal to the angle of reflection.

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