p14

Question 1

what are three wave transfers?

Answer 1

absorption
reflection
transmittion

Question 2

law of reflection?

Answer 2

angle of incidence = angle of reflection

Question 3

describe specular reflection

Answer 3

when the boundary is flat so all the normals point in the same direction therefore a clear image is formed

Question 4

describe diffuse reflection

Answer 4

when the boundary is bumpy or rough so all the nromals are different therefore light is reflected in different diections, forming a not so clear image

Question 5

refraction changes

Answer 5

in a more dense object, the waves travel slower. this means that on a diagram, they would bend closer to the normal.

Question 6

what are transparent objects?

Answer 6

they transmit all incidnet light that enters the object

Question 7

what are translucent objects?

Answer 7

objects that let light pass through them, but the light is scattered or refracted.

Question 8

what is a convex lens?

Answer 8

it makes parallel rays converge to a focus. it is used as a magnifying glass and in a camera to form a clear image of a distant object.

Question 9

what is a concave lens?

Answer 9

makes parallel rays diverge (spread out). it is used to correct short sightedness.

Question 10

principle focus in convex lens

Answer 10

where the parallel rays are focused to

Question 11

principle focus in concave lens

Answer 11

where the rays appear to come from

Question 12

what is focal length?

Answer 12

the distance from the centre of the lens to the principle focus

Question 13

how is an image formed?

Answer 13

its formed at points where all light rays from a point on an object comes together.

Question 14

what is a real image?

Answer 14

when light rays come together to form an image and it can be captured on a screen. normally the image is inverted.

Question 15

what is a virtual image?

Answer 15

formed from where light rays appear to come from (concave). the image is upright and smaller.

Question 16

wave speed equation

Answer 16

wave speed = frequency x wavelength

Question 17

magnification equation

Answer 17

magnification by lens = image height/object height

Question 18

why does red light on blue object make the object black?

Answer 18

only red light is transmitted by the filter. the red is absorbed by the blue object so no light is reflected by the blue object.

Question 19

how do colour filters work?

Answer 19

they work by absorbing certain wavelengths and transmitting other wavelengths

Question 20

what happens when white light is passed through a red filter?

Answer 20

all the other wavelengths of colours are absorbed, but red light is transmitted.

Question 21

when will an object appear black?

Answer 21

if all wavelengths are absorbed

Question 22

when will an object appear white?

Answer 22

if all wavelengths are reflected equally

Question 23

explain refraction practical

Answer 23

• place a glass block on a piece of paper
• draw around the glass block
• use the ray box to shine a ray of light through the glass block
• mark the ray of light entering the glass block
• mark the ray of light emerging from the glass block
• join the points to show the path of the complete ray through the block
• and draw a normal line at 90 degrees to the surface
• use a protractor to measure the angle of incidence
• use a protractor to measure the angle of refraction
• use a ray box to shine a ray of light at a range of different angles (of incidence)
• increase the angle of incidence in 10 degree intervals
• from an angle of incidence of 10 degrees to an angle of incidence of 70
  degrees.