Physics Grade 10 Topic 1-5

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Sources of light

Light is a spectrum- meaning some light is visible

There are countless sources of light, but they can all be categorized under either of the two following categories-

Natural sources

Objects that emit light for example the sun, moon, stars and some living organism by bioluminescence.

Artificial sources

Light can artificially be created under three BROAD categories

Incandescent sources- when certain objects are heated to a high temperature they emit light. Both infrared and visible light is produced. Ex. Candle.

Luminescent sources- produced by accelerating charges in a luminescent material, bypassing current through the material. Ex. Electric Bulb.

Gas discharge sources- when electricity passes through certain gases at low pressure. light is produced. Ex. Neon lamp.

Frequency: Number of waves that pass in a certain period of time

Wavelength: Distance between two corresponding points on adjacent waves

If the frequency is high, the wavelength is shorter. Whereas if the wavelength is bigger, f is lower

Speed of light is about 3.00 x 10^8m/s

Other types of light emission:

Fluorescence- emission of light from a substance that has absorbed light

Phosphorescence- energy absorbed by substances then released slowly, glow in the dark

Chemiluminescence- light is the product of a chemical reaction, two high energy chemicals break down to release light

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Light and Reflection

Law of reflection

The angle of incidence is equal to the angle of reflection

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

Reflection- the change in direction of light waves when it bounces off a surface

Medium- substance through light travels

Ray- straight line that shows how light travels and which direction indicated by arrows

Incident ray- from light source/ object to surface/ mirror

Normal- perpendicular line to the surface, shows where ray of light meets surface

Reflected ray- begins where the point of incident ray and normal meet

Angle of incidence- angle between incident ray and normal

Angle of reflection- angle between reflected ray and normal

Plane Mirror- mirror with a flat reflected surface

Virtual image- image formed by rays that seems to be coming from a position but isn't, not real.

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Images in a Plane Mirror

SOLT

Size will always be the same

Orientation will always be upright

Location will be the same as they are the same distance away

Type of image will always be inverted

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Images in Concave Mirrors

SOLT

Size depends could be bigger or smaller

Orientation is generally inverted

Location is either behind C, on C, between C and F, on F, or ahead of F

Type of image is most likely real

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Image in Convex Mirrors

SOLT

Size is smaller

Orientation is upright

Location is between vertex and focal point

Type is always virtual