Physics - waves (mixed subjects)

Question 1

what is absorbtion

Answer 1

when waves are absorbed into the material, transferring the energy into the materials energy stores.

Question 2

what is reflection

Answer 2

when waves bounce back from a surface.

Question 3

what is transmission

Answer 3

when waves travel through a material.

Question 4

what is optical density

Answer 4

how quickly light travels through a material.

Question 5

what is the refractive index

Answer 5

a measure of optical density, the bigger the refractive index, the more optically dense a material is.

Question 6

what are wavefronts

Answer 6

imaginary lines drawn on a ray diagram showing wavelength.

Question 7

what are the two types of reflection

Answer 7

specular and diffuse

Question 8

what is specular reflection

Answer 8

when a ray reflects off a smooth surface and show a clear image.

Question 9

what is diffuse reflection

Answer 9

when a ray reflects off a rough surface and it scatters.

Question 10

why do rays scatter off a rough surface

Answer 10

the normal for each ray is different and so the angle of reflection is different for each ray.

Question 11

why do opaque objects appear opaque

Answer 11

they absorb most wavelengths of light and reflect the rest.

Question 12

why does a green hat appear black through a red filter

Answer 12

because the hat absorbs all light wavelengths that do not correspond to the colour green.

Question 13

what is a black body

Answer 13

an object that absorbs all of the EM radiation that hits it.

Question 14

define intensity

Answer 14

power per unit area

Question 15

what objects emit radiation

Answer 15

all objects

Question 16

name three rules about convex lenses

Answer 16

1) a ray travelling parallel to the axis will refract through the lens and intercept the principal focus.
2) a ray travelling through the middle of the lense will not refract it will continue in a straight line.
3) a ray that intercepts the principal focus before the lens will refract through the lens and leave parallel to the axis.

Question 17

how do you find the principal focus on concave lens

Answer 17

where it looks like all the emerging rays would meet diverge. you can trace the emerging rays to a single point using virtual rays.

Question 18

what is the focal length

Answer 18

the distance between the centre of a lens and the principal focus

Question 19

what are three rules about concave lenses

Answer 19

1) an incident ray travelling parallel to the axis will emerge in a straight line to the principal focus
2) an incident ray travelling through the middle of the lens will continue in a straight line.
3) an incident ray passing towards the far side principal focus will emerge parallel to the axis.

Question 20

what is a “real image”

Answer 20

when light rays from a point on an object come together to form an image.

Question 21

what is a “virtual image”

Answer 21

when light rays from a point on an object are diverging after they have left the lens.

Question 22

what three things do you need to say to describe an image

Answer 22

how big it is compared to the object.
whether it is upright or inverted in relation to the object.
whether it is real or virtual.

Question 23

what sort of images to convex lenses produce.

Answer 23

real or virtual

Question 24

what sort of images to concave lenses produce

Answer 24

virtual

Question 25

what happens to a ray that goes through the centre of a lens

Answer 25

nothing, it continues in a straight line.

Question 26

what do convex lenses do to light

Answer 26

converge it

Question 27

what do concave lenses do to light

Answer 27

diverge it