Light

Question 1

What are luminous sources

Answer 1

Sources that produce or give out light of their own

Question 2

How can we see objects which are not luminous?

Answer 2

Light rays hit the object and are reflected into our eyes

Question 3

Draw diagram of right ray passing through a concave prism and name the type of ray

Answer 3

diverging

Question 4

Draw a ray passing through a convex prism and describe the ray

Answer 4

converging

Question 5

What are the three types of rays?

Answer 5

converging >

diverging <

parallel =

Question 6

Evidence for light travelling in straight lines and phrase used?

Answer 6

shadows

pinhole camera

light in a lazer beam

light streaming through branches

rectilinear propagation

Question 7

In a pinhole camera the image is:

Answer 7

inverted (upside down), real (formed on a screen)

Question 8

1. In the pinhole camera the image is quite dim, how do you make it brighter and what else will happen?
2. What happens if the pinhole is made bigger?

Answer 8

1 Move object closer and image becomes bigger and brighter.

2 Image becomes fuzzy (less clear).

Question 9

How are shadows formed?

Answer 9

When opaque objects stop light from reaching an area.

Question 10

Draw a diagram to illustrate a shadow produced from a point source. What is the shadow like and called?

Answer 10

UMBRA - a sharp and completely dark shadow

Question 11

Draw a diagram to illustrate a shadow produced from an extended light source. What is the shadow like and called?

Answer 11

Umbra and PENUMBRA formed.

Penumbra is dim and not shaped, it is a partial shadow.

Question 12

What is the law of reflection? Illustrate using a diagram.

Answer 12

Angle of incidence equals the angle of reflection, all angles taken from the normal.

Question 13

Show how a periscope works

Answer 13

angle of mirrors is 45 degrees

Question 14

Draw a diagram to illustrate a mirror image.

Answer 14

Make sure to label and show direction of light.

Question 15

Properties of the image in a plane mirror:

Answer 15

same size, upright, laterally inverted, same distance behind mirror as it is in front.

Question 16

Draw a diagram to illustrate refraction of light passing through a glass block.

Answer 16

remember to label emergent angle and that it is parallel to the incident angle.

Question 17

What happens as the light passes into a glass block?

Answer 17

Light ray enters more optically dense medium e.g. air to glass, the ray slows down and bends towards the normal.

When light leaves more optically dense medium e.g. glass to air, the ray speeds up and bends away from the normal.

Question 18

How are all colours made?

Answer 18

primary colours etc.

Question 19

How is the colour of an object/filter produced?

Answer 19

Colours not absorbed are reflected.

Question 20

Show how an object appears when placed in water.

Answer 20

how normal

Question 21

ilustrate light passing through a glass prism and explain what happens

Answer 21

The different colours of white light are refracted by different amounts as they enter the triangular prism. The change of direction is called DEVIATION. Splitting of colours is called DISPERSION.