Light 🔦

Light is an energy jo enables us to see

Reflection bouncing back of light from a surface in the same medium

Laws of reflection:

1. Angle of Incidence = Angle of Reflection

2. Incident ray, Reflected ray & Normal lie on the same plane

   

If the angle between surface and incident ray = 30, the angle of reflection = 90 - 30 degree not 30

If the light ray falls like this, <i is 0 degree, so <r = 0 degree too

Regular reflection: When a beam of parallel rays is incident to a smooth surface, the reflected rays r also parallel

Diffused reflection : When a beam of parallel rays is incident on a rough surface, the rays get reflected in diff directions

• Diffused reflection follows laws of reflection

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Mirror 🪞: Polished shiny surface jo changes direction of light

Properties of image formed by plane mirror:

• Virtual & Erect

• Laterally inverted

• Same size of the Object

• Distance between object & mirror = Distance between mirror & image

  Multiple image formation: When 2/ more mirrors r placed at different angles we get multiple images

• Applications of this -

  1. Periscope : helps us to see objects that r not in direct line of sight

     submarines me use hota hai

     

2. Kaleidoscope: Reflect light through mirrors to form patterns

Dispersion Of Light: White light is made of 7 colours

Used in rainbows, prisms etc

The dispersed light forms a spectrum

Red bends least & Violet bends the most

Human Eye:

1. Cornea: Maximum bending of light happens in cornea

   Also protects the eye

2. (In cornea) Pupil: window of eye, light enters through this

   Changes its size, in birght its small & dark, its bigger

   muscles control the size of pupil

3. Iris: Colour of the eye

   Muscles in the iris control size of pupil

4. Lens ( in Iris ): Helps in forming image

5. Ciliary Muscles: Eye lens can become thin & thick

   These muscles control thickness & curvature of the lens

   They contract and make it thicker, & relax and make it thineer

6. Retina: Screen of the eye where image is formed

   • Has 2 types of cells

     i. Rods: Sensitive to light intensity, helps to see in dark

     ii. Cones: Sensitive to colour

7. Optical Nerve: Take the image formed on retina to the brain in the form of electrical signals and brain interprets it

8. Blind spot : Where optical nerves form a bundle and to towards the brain

   • Here there r no photo receptors, so image isn’t formed

Defects In Vision:

1. Nearsightedness - Myopia: objects near r clear but far objects aren’t

2. Farsightedness : Far objects r clear but near objects aren’t

3. Cataract : Eye lens becomes opaque

To take care of eyes:

• good food ( vit A rich)

• Dont rub eyes too often

• Read from atleast 20 cm distance

Braille System: Invented by Louis Braille

• System of reading & writing by touch, used by ppl with low vision