Reflection of Light

When light from a source (like the sun or a bulb) falls on an object, it bounces back from the surface. This bouncing back of light is called reflection. We are able to see objects because the reflected light reaches our eyes.

• For example, mirrors, glass pane, sunglasses, etc. These surfaces are smooth and shiny, allowing them to reflect light evenly.
• When light reflects evenly, it forms a clear image. Surfaces that are rough or dull scatter light in different directions, preventing a clear image from forming.

Understanding How Light Helps Us See and Reflection of Light:

• In a dark room at night, turning off the light makes objects invisible.
• When the light is turned on, objects become visible again.
• This happens because light enters our eyes, allowing us to see.
• Light can be emitted by an object (e.g., a bulb) or reflected off an object.
• Reflection occurs when light rays bounce off objects and reach our eyes.
• This activity shows that vision depends on light and that non-luminous objects are seen due to reflection.

1. Aim: To study the reflection of light and understand the terms related to it.

2. Requirements: torchlight, mirror, stand for hanging the mirror, black paper, comb, white paper, and drawing board.

3. Procedure

• Attach a white paper to a table or a drawing board.
• Cover most parts of the comb with black paper, leaving a small open portion in the middle for light to pass through.
• Hold the comb perpendicular to the white paper and direct the torchlight through the open portion of the comb.
• Place a mirror in the path of the light rays coming through the comb.
• Observe how the light rays behave when they hit the mirror.

Draw the setup on the white paper:

• Draw a straight line (PQ) to represent the mirror.
• Mark the incoming ray (incident ray, AO), reflected ray (OB), and normal line (ON) perpendicular to the mirror at the point of incidence (O). As ON is perpendicular to PQ, ∠PON = ∠QON = 90°.
• The angle ∠AON between the incident ray and the normal is the angle of incidence (i)
• The angle ∠BON between the reflected ray and the normal is the angle of reflection (r)

Reflection of light

4. Observations: The light rays falling on the mirror (incident rays) bounce back in another direction (reflected rays). The reflected rays follow specific rules based on the angle of incidence and the angle of reflection.

5. Conclusion: The incident ray, reflected ray, and normal all lie in the same plane. The angle of incidence (∠AON) is always equal to the angle of reflection (∠BON). This demonstrates the laws of reflection, which govern how light reflects off surfaces.

• Reflection occurs when light bounces off a smooth surface like a mirror, following fixed laws.
• Plane mirrors always form virtual, erect, and same-sized images that are laterally inverted.
• Curved surfaces (like a spoon) act as spherical mirrors, changing the image size and orientation depending on the object's position.

The phenomenon of bouncing back of light rays in the same medium on striking a surface is called reflection of light.

• The angle of incidence ∠i = angle of reflection ∠r.
• The incident ray, reflected ray, and normal lie in one plane; both rays are on either side of the normal.

n = \[\frac {360°}{θ}\]

• If n is even → N = n − 1
• If n is odd → N = n (object not on bisector); N = n − 1 (object on bisector)
• If n is a fraction → N = integral part of n