Light

What is light

a form of energy allowing us to see

what is the main source of light

the sun

why can we not see around corners?

because light travels in straight lines

Light Ray

the direction of the path that the light is travelling in.

Beam

A collection of light rays

A beam can be _________, _________, or ___________.

parallel, divergent, convergent

Luminous objects

those which can emit their own light (the sun, a candle, a lightbulb)

Non-luminous objects

those which cannot emit their own light (the moon, a chair, a human)

Opaque materials

do not allow any light to pass through them (wood, a mirror, humans)

How do shadows form

when opaque materials block light

Translucent materials

only allow for a certain amount of light to pass through them (vegetable oil, tinted car windows, wax paper)

Transparent materials

allow for all light rays to pass through them (glass, air, water)

Reflection:

when light rays bounce off of an opaque surface

2 types of reflection

regular & diffuse

Regular reflection

only happens with a smooth, opaque surface like a mirror where all light rays will reflect perfectly into your eye.

Diffuse

light rays will be scattered due to a rough surface, like paper where only some of the light rays will reflect into your eye.

Law of Reflection:

The angle of incidence = the angle of reflection

When you look in a plane (flat) mirror everything is the same, except your reflection is laterally inverted, meaning

that your left appears as your right and vice versa in a mirror

We see an image when

light is reflected off of a smooth surface and travels into your eye

There are 2 types of images:

Real & virtual

Real Image

can be produced on a screen.

Virtual image

cannot be produced onto a screen and doesn’t exist behind the mirror.

Refraction:

This is the bending of light rays as it travels through different media

Light rays refract because

they travel in straight lines but pass through different media (materials) at different speeds.

Lenses:

This is a transparent piece of glass that can refract light

There are 2 types of lenses:

Concave lens (Diverging Lens) & Convex Lens (Converging Lens)

Concave lens

These curve inwards so it is thinner in the middle

concave lenses are known as a diverging lens because

it causes light rays to spread out in different directions

If a concave lens is used to produce an image on a screen, it will give

a smaller, upright image.

Concave lenses can correct myopia (near-sightedness) which is when

distant objects appear blurred as light rays are refracted too much and become focused in front of the retina

Convex Lens:

This lens curves outwards meaning it is fatter in the middle.

Convex lens is called a converging lens because

it causes light rays to come together at a point

If a convex lens is used to produce an image it will produce a

larger, upside-down image.

Convex lenses can correct hypermetropia (far-sightedness) which is when

objects appear blurred because light rays are not refracted enough and become focused behind the retina