Light
Light is a form of energy which produces the sensation of sight. When a light rays travels from rarer to a denser medium, it bends towards the normal. This note gives us the information about light and refraction of light.
Summary
Light is a form of energy which produces the sensation of sight. When a light rays travels from rarer to a denser medium, it bends towards the normal. This note gives us the information about light and refraction of light.
Things to Remember
- Light is a form of energy which produces the sensation of sight.
- The main source of heat and light energy in the earth is sun.
- The bending of light as it passes from one medium to another medium is called refraction of light
- When a light rays travels from rarer to a denser medium, it bends towards the normal.
- When the light passes along the normal i.e. at right angle to the surface, it passes without deviation
MCQs
No MCQs found.
Subjective Questions
Q1:
B. Rewrite the following sentences in the correct order;
i. Mother ran fast to go upstairs.
ii. The boy's legs slipped through the gap of the grille.
iii. Vikram has managed to catch the boy.
iv. The boy was trying his best to be comfortable.
Type: Very_short Difficulty: Easy
Q2:
C. Answer the following questions:
i. Why did Neha leave her child alone at home?
Type: Short Difficulty: Easy
Q3:
C. Answer the following questions:
ii. What caused the boy to fall from the window?
Type: Short Difficulty: Easy
Q4:
C. Answer the following questions:
iii. Why did Neha run upstairs to her bed-room?
Type: Short Difficulty: Easy
Q5:
C. Answers the following questions :
iv. For what purpose was a bed-cover demanded from the crowd?
Type: Short Difficulty: Easy
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Light
Light is a form of energy which produces the sensation of sight. The main source of heat and light energy in the earth is the sun.
Refraction of light
The bending of light as it passes from one medium to another medium is called refraction of light.
Laws of refraction of light
- The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.
In the figure, the incident ray AO refracted ray OB and normal ray MN at the point of incidence O; all lie in the same plane.
- The ratio of the sine of the angle of refraction is constant for a given pair of media. This is also called Snell’s law.
Mathematically,
i.e 
In the figure,∠ i is the angle of incidence in the air and ∠ r is the angle of refraction. In another medium glass in which the light enters. The ‘constant’ is called refractive index (R.I.) of the glass where light enters. It is denoted by µ.
The Snell’s law can be stated in the following ways:
- When a light rays travel from rarer to a denser medium, it bends towards the normal. It means the angle of incidence is greater than the angle of refraction.
- When the light passes from a denser to a rarer medium, it bends away from the normal. It means the angle of incidence (∠i) is smaller than the angle of refraction (∠r).
- When the light passes along the normal i.e. at a right angle to the surface, it passes without deviation.
Lesson
Light
Subject
Science
Grade
Grade 9
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