Physics - Unit 12

Light Source

A light source is an object that emits its own light.

The Law of Reflection

The law of reflection tells us about the direction in which the ray of light is reflected.

Incident Ray

The ray of light coming in.

Light travels in ————.

straight lines

The Angle of Reflection

The angle between the normal line and the reflected ray.

Reflection

The bouncing back of a ray of light when it strikes the surface of a non-transparent/reflective material.

Luminous

An object which is a source of light is described as luminous.

Critical Angle

Critical angle means the angle of incidence which gives 90° for the angle of refraction.

Non-luminous

An object which is not a source of light is described as non-luminous.

When a ray of light enters a transparent material, it……

Why do we see a clear image in a mirror?

A mirror has a very flat, smooth surface. Rays of light bounce off the mirror without being scattered.

Why don’t we see a clear image in a sheet of paper?

A sheet of paper has a rough surface. When rays of light strike the paper, they are scattered in all directions.

Normal

The normal is a straight line drawn at the right angle of 90° to the mirror at the point where the ray is reflected.

Explain Dispersion

Dispersion happens because of refraction. When white light enters a glass block, some colours bend more than others. Violet bends the most, red bends the least. This means that different colours travel off in different directions, and so we can see them separately.

Law of reflection equation

angle of incidence = angle of reflection

When a ray of light leaves a transparent material, it……

Dispersion

The splitting up of white light into a spectrum of separate colours is called dispersion. The colours of the spectrum always appear int eh same order : Red, Orange, Yellow, Green, Blue, Indigo, Violet.

Angle of Incidence

The angel between the normal line and the incident ray.

Reflected Ray

The ray of light going out.

Refraction

The change of direction of a light ray when it enters of leaves a transparent material is called refraction.

If you can see a clear reflected of yourself in an object, what does this tell you about the surface of the object?

The surface of the object must be very smooth.

A prism is a ———.

triangular glass block

How does refraction work?

The ray bends at the point where it enters a transparent material and at the point where it leaves the material. It follows a straight path in the material.

Total Interval Refraction is when…..

the angle of incidence is greater than the critical angle, leading the refracted angle into the transparent material.