Light

Light

a form of energy that travels away from the source that produces it at a speed of 3×10^8 m s-1

Crooke’s Radiometer

converts light into kinetic energy, which proves light is a from of energy

Parallel Beam

rays of light that travel in straight lines that never touch

Converging Beam

rays of light that travel inwards which eventually meet at a point

Diverging Beam

rays of light that travel outwards which never meet

Reflection

the bouncing of light from the surface of an object

Diffuse Reflection

light reflected from a matt surface is scattered in all directions

Regular Reflection

light reflected from a smooth surface is reflected directly

First Law of Reflection

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

Second Law of Reflection

the angle of incidence is equal to the angle of reflection

Image in a Plane Mirror

virtual, upright, the same distance behind the mirror as the object is in front of the mirror. objects are laterally inverted.

Parallax

the apparent movement of on object relative to another due to the motion of the observer. the object that is farthest away appears to move with the observer

Concave Mirror

reflecting surface caves in at centre

Convex Mirror

reflecting surface bulges out at centre

Concave Mirror - Ray at Pole

reflected at an equal angle with the axis

Concave Mirror - Ray Through Centre of Curvature

reflected back along its path

Concave Mirror - Ray Parallel to Axis

reflected through focus

Concave Mirror - Ray Through Focus

reflected parallel to axis

Real Image

an image formed by the actual intersection of rays, can be formed on a screen

Uses of a Concave Mirror

dentist’s mirror, floodlights, projector, torch, solar furnace, cosmetics mirror

Concave Mirror - Image Outside Focus

real, magnified, upside down

Concave Mirror - Image on Focus

formed at infinity

Concave Mirror - Image Inside Focus

virtual, magnified, upright

Concave Mirror - Image Outside Centre of Curvature

real, diminshed, upside down

Virtual Image

image formed by the apparent intersection of rays

Convex Mirror - Ray at Pole

reflected at an equal angle with axis

Convex Mirror - Ray Towards Centre of Curvature

reflected along back its own path

Convex Mirror - Ray Parallel to Axis

reflected as if coming from focus

Convex Mirror - Ray Towards Focus

reflected out parallel to axis

Refraction

the bending of light when it goes from one medium to another

Light from Rarer Medium to Denser Medium

refracted towards the normal

Light from Denser Medium to Rarer Medium

refracted away from the normal

First Law of Refraction

the incident ray, the normal at the point of incidence and the refracted ray all lie in the same plane

Second Law of Refraction

the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant

Snell’s Law

states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant

Refractive Index

the ratio of the sine of the angle of incidence to the sine of the angle of refraction when light travels from air into that material

Apparent Depth

due to refraction an object in liquid appears at a lesser depth than it actually is

Decrease in Apparent Depth

happens when object is viewed more from the side, apparent depth is greatest when viewed vertically above

Critical Angle

When light travels from a denser to a rarer medium the angle of incidnce whose angle of refraction is 90 degrees is called the critical angle

Total Internal Reflection

when light going from a denser to a rarer medium strikes the rarer medium at an angle greater than the critical angle, it does not enter the second medium, it is all reflected back in the denser medium

Optical Fibres

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