science chapter 5

What are luminous objects?

sources of light

What are non-luminous objects?

objects that do not produce light

light travels in __

straight lines

what do we use to represent light?

straight lines called rays

what is a ray?

a thin line of light

what is a beam?

a stream of light rays

light travels from __ to __

the object to our eyes

What does a ray diagram do?

traces the path light takes from the object to the observer/eye

How can we see luminous objects?

they emit light, which enters our eyes

How can we see non-luminous objects?

light reflects off them and into our eyes

What is the ‘object’ we see in mirrors called?

image

characteristics of images formed in plane mirrors:

same distance from mirror as object, same size as object, upright, virtual and laterally inverted

What is a normal?

a dotted line perpendicular to the surface

What is the angle of incidence?

angle between incident ray and normal

what is the angle of reflection?

angle betwene reflected ray and normal

State the law of reflection

The angle of incidence is equal to the angle of reflection

Image on mirror must be __

dotted

How can you change the direction that a light ray travels?

Use more than one mirror

What does a periscope do?

uses two mirrors to allow us to see over obstacles

When you look through a periscope, why is the image upright?

Plane mirrors do not change the vertical orientation of the object, image remains upright

When looking through a periscope, will the image be laterally inverted?

No. 2 mirrors are used so there are 2 lateral inversions

suggest other uses for a periscope

to see over a crowd of people, for military purposes

What is a convex?

A curved mirror that bulges outwards

What is a concave?

A curved mirror that bulges inwards (creating a ‘cave’)

in convex and concaves mirrors, the images have __ proportions

distorted

concave mirrors make the size of the image __ and field of vision __

bigger

convex mirrors make the size of the image __ and field of vision __

smaller

What is refraction?

the bending of light when light travels from one transparent medium to another due to a change in the speed of light

Light travels __ in optically denser materials

slower

A ray of light bends __ the normal when it enters an optically denser medium

towards

A ray of light bends __ the normal when it enters a less optically dense medium

away

If a light ray enters another medium perpendicularly to the boundary, what happens?

No deviation of the ray is observed

What is the effect of refraction?

makes objects under glass or water appear closer than they really are