science chapter 5 ray model of light

light

How fast can light travel in a vacuum (e.g. outer space)

300 000 000m/s

Three types of electromagnetic radiation

Ultraviolet radiation
Visible light
Infrared radiation

Harmful effects of ultraviolet radiation

Overexposure can harm our eyes and can cause skin cancer

Harmful effects of visible light

deterioration of paintings, photos
Light pollution, affects living things (e.g. migratory birds) and humans' sleep cycle

Harmful effects of infrared radiation

Overexposure can cause harm to the body
infrared radiation trapped in the atmosphere contributes to climate change

Applications of ultraviolet radiation (for …. …………… , ……. and …… which is …….)

For disinfecting medical equipment, food and water which is more environmentally friendly than using harmful chemicals

Applications of ultraviolet radiation (babies)

For treating babies with certain medical conditions

Applications of ultraviolet radiation (helps …………… the …………………… of ……………… …)

Helps increases production of vitamin D

Applications of visible light (plants …….., allows us to………)

Plants rely on visible light to photosynthesize and allows us to carry out daily activities

Applications of infrared radiation (……………………. ………………. to ………. …………… in the ………….)

Night-vision cameras to take pictures in the dark without flash

Applications of infrared radiation (infrared ……………. ………………..)

infrared remote controllers

Applications of infrared radiation

Used in healthcare (e.g. thermal screening to screen people with fever)

Which coloured light rays bends the most and least

Violet rays bend the most while red rays bend the least

Dispersion of light

White light is made up of the colours red, orange, yellow green, blue, indigo and violet

Objects in an optically more dense medium (e.g. water) seem to be ______than they actually are

shallower

What can be formed if regular reflection occurs

Clear images

Irregular reflection

Occurs when parallel light rays fall on a rough surface and each ray is reflected in a different direction

Why are there no clear images formed during irregular reflection

A rough surface scatters light

What happens to a light ray travelling from an optically less dense (e.g. air) medium to an optically more dense (e.g. glass) medium

The light ray bends toward the normal

What happens to a light ray travelling from an optically more dense (e.g. water) medium to an optically less dense (e.g. air) medium

The light ray bends away from the normal

5 objects ordered from optically less dense to more dense

Vacuum, air, water, glass and diamond

relationship between optical density of a medium and the rate of light travelling

The higher the optical density of a medium, the slower light travels through the medium

What can change in speed of light cause

Change in direction of light ray

Normally incident ray

Ray that is perpendicular to the surface
No bending of the ray is observed even when it enters another medium

Emergent ray

Ray that leaves the optically denser object

Is emergent ray a refracted ray, why

Yes, because it is the ray that comes out of an optically denser object so the light will bend away from the normal since it is now out of the medium

plane mirror image facts

image is virtual
image is upright
image is laterally inverted (reverses left and right side of object image)
image is the same size as object
image in the mirror cannot be formed on a screen

which surface does reflection occur

smooth and flat surfaces

How are shadows formed

When light is blocked

How do we see non-luminous objects

Light is reflected of off their surfaces

Laws of reflection

The incident ray, reflected ray and the normal all lie on the same plane
The angle of incidence is equal the the angle of reflection

Angle of incidence

Angle between incident ray and the normal at the point of incidence

Angle of reflection

Angle between reflected ray and the normal at the point of incidence

Normal

Imaginary line perpendicular to the reflective surface

Incident ray

Light ray hitting the reflecting surface

Reflected ray

Light ray travelling away from the reflecting surface after bouncing off the surface

Why are virtual images called virtual images

The reflected rays of the object appear to have come from the image in the mirror

Field of view

How wide a view we can see in a mirror

Convex mirrors facts

They form virtual upright and dimished (smaller) images

What are convex mirrors usually used for

Used when a large area needs to be seen

What kind of field of vision do convex mirrors provide

Wider field of vision

Concave mirrors facts

They form virtual, upright and magnified (larger) images

What kind of field of vision do concave mirrors provide

Smaller field of vision

What are concave mirrors usually used for

Used when a magnified image is needed

Regular reflection

Occurs when parallel light rays fall on a smooth surface and reflected in the same direction

Why does refraction occur

Due to a change in speed of light(increase/decrease) as it passes from one material to another

Concave mirrors

mirrors that curve inwards

Convex mirrors

mirrors that curve outward

Virtual image

Mirror image

Objects that can emit light on their own

Luminous objects

Plane mirrors

mirrors that are flat and smooth

reflection

Light bouncing off a surface

refraction

bending of light when it enters another transparent medium

ray model of light

using a straight line to represent the way light behaves