What are the Laws of Reflection of Light? | Physics | Don't Memorise

Summary

This video explains the behavior of light, particularly how we see objects due to light reflection. It differentiates between luminous objects, which emit their own light, and non-luminous objects, which reflect light. The video introduces the concept of light rays and discusses the laws of reflection. The first law states that the angle of incidence equals the angle of reflection, while the second law asserts that the incident ray, reflected ray, and normal all lie in the same plane. The video sets the stage for a hands-on experiment to demonstrate these principles.

Takeaways

• 😀 Light is visible because of its reflection from objects, and some objects like the Sun, burning candles, and fluorescent bulbs emit their own light (luminous objects).
• 😀 Non-luminous objects do not generate their own light but reflect light from luminous objects, allowing us to see them.
• 😀 Light emitted by luminous objects travels in all directions, which is represented by rays of light.
• 😀 A ray of light is a straight-line path along which light travels.
• 😀 When light strikes a surface, it is reflected according to specific laws of reflection.
• 😀 The incident ray is the ray of light that strikes a surface.
• 😀 The reflected ray is the ray of light that bounces off the surface after reflection.
• 😀 A perpendicular line called the 'normal' is drawn at the point where the light ray strikes the surface.
• 😀 The first law of reflection states that the angle of incidence (I) is always equal to the angle of reflection (R).
• 😀 The second law of reflection asserts that the incident ray, reflected ray, and normal all lie in the same plane.
• 😀 Any violation of these laws, such as rays not lying in the same plane, would not result in valid reflection according to the laws of light.

Q & A

What is the difference between luminous and non-luminous objects?

Luminous objects emit their own light, such as the Sun, burning candles, and fluorescent bulbs. Non-luminous objects do not generate light but reflect light from luminous objects, allowing us to see them.

What is a ray of light?

A ray of light is a straight line path along which light travels. It is represented by a straight line with an arrow pointing in the direction of the light's travel.

What happens when light rays from a luminous object, like a fluorescent bulb, strike a non-luminous surface?

When light rays from a luminous object strike a non-luminous surface, the rays are reflected. These reflected rays travel in a specific direction according to the laws of reflection.

What is an incident ray?

An incident ray is the ray of light that strikes a surface. It is the incoming ray before it is reflected by the surface.

What is a reflected ray?

A reflected ray is the ray of light that bounces off the surface after striking it, traveling in a direction defined by the laws of reflection.

What is the normal line in the context of light reflection?

The normal is a perpendicular line drawn at the point of incidence, where the incident ray strikes the surface. It is used as a reference to measure angles of incidence and reflection.

What is the angle of incidence?

The angle of incidence is the angle formed between the incident ray and the normal line at the point where the light strikes the surface.

What is the angle of reflection?

The angle of reflection is the angle formed between the reflected ray and the normal line after the light has been reflected by the surface.

What are the two laws of reflection?

The first law of reflection states that the angle of incidence is always equal to the angle of reflection (I = R). The second law states that the incident ray, reflected ray, and normal all lie in the same plane.

Why must the incident ray, reflected ray, and normal lie in the same plane?

The incident ray, reflected ray, and normal must lie in the same plane for the reflection to obey the laws of reflection. If they don't, the reflection would not follow the expected behavior, which would violate the second law of reflection.