01. Light

Light is a form of energy
that travels away from the
source producing it at a
speed of about 3 x 10⁸ m s⁻¹ .

The bouncing of light off an object

Law 1: The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

Law 2: The angle of incidence is equal to the angle of reflection.

The apparent movement of one object relative to another due to the motion of the observer

*Emit their own light

*Do not emit their own light but reflect light from their surface

an image formed by the actual intersection of light rays.

An image formed by the apparent intersection of rays.

The bending of light as it passes from one medium to another

1) The incident ray, the normal and the refracted ray all lie in the same plane.

2) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant .

i.e. n = Sin i ÷ Sin r , where n is a constant

The ratio of the sine of the angle of incidence to the sine of the angle of refraction

the ratio of the sine of the angle of incidence to the sine of the angle of refraction when light travels from one of those media into the other.

The angle of incidence whose corresponding angle of refraction is 90°

Occurs when the angle of incidence in the denser medium exceeds the critical angle and all the light is reflected back into the medium.

OR **(Learn 1)**

When light going from a denser to a rarer medium strikes the second medium with an angle of incidence greater than the critical angle, it does not enter the second medium.
It is all reflected back in the denser medium. This is called total internal reflection.

A very thin transparent rod through which light can
travel by total internal reflection

*If two lenses of power P1 and P2 are placed in contact, the power P of the combination is given by:
P = P1 + P2



If two lenses of focal length f1 and f2 are placed in contact the focal
length f of the combination is given by:

1/f = 1/f1 + 1/f2

Where f is given a ‘+’ sign for a converging lens and a ‘–’ sign for a diverging lens.

*A short-sighted person can see nearby objects clearly but cannot bring distant objects into focus.

Fixed with a diverging lens

*A long-sighted person can see distant objects clearly but cannot bring
nearby objects into focus.

Fixed with a converging lens

The Power of Accommodation: of the eye is its ability to focus on objects at different distances by changing the shape of the lens

*n = sin i ÷ sin r

n = c1 ÷ c2

n = 1 ÷ sin C

n = Real Depth ÷ Apparent Depth

* 1)Always through C straight through

2&3) If parallel to floor, then goes through F & vice versa
BUT Diverging lens: other side of mirror

* 1) ALWAYS through centre of lens straight through

2) Parallel to floor
Converging: to f on other side
Diverging: to f on same side

*
– (1 ÷ f) = (1 ÷ u) – (1 ÷ v)