Light waves, em. spectrum and lens

Question 1

Name 4 properties of images in plane mirrors.

Answer 1

• upright
• virtual (real light rays do not come together)
• laterally inverted
• same size as object
• image is same perpendicular distance behind the mirror as the object is in front

Question 2

Is an image in a plane mirror real or virtual?

Answer 2

virtual (real light rays do not come together)

Question 3

What happens to light as it enters a different medium?

Answer 3

changes speed and direction

Question 4

When light goes from a LESS dense to a MORE dense medium, what happens to the refraction?

Answer 4

refraction is towards the normal
i>r

Question 5

When light goes from a MORE dense to a LESS dense medium, what happens to the refraction?

Answer 5

refraction is away from the normal
i<r

Question 6

What happens in refraction when the angle of incidence is 0?

Answer 6

no refraction

Question 7

What is the critical angle?

Answer 7

angle between incident ray and normal, when the refracted ray is parallel to mediums surface

Question 8

What is refractive index (n)?

Answer 8

the ratio of the speeds of a wave in two different regions

Question 9

What causes total internal reflection?

Answer 9

when angle of incidence is greater than the critical angle
when wave speeds up after crossing boundary

Question 10

How does an optic fibre work in telecommunication?

Answer 10

used to transmit optical pulses over long distances
short pulse of light produced at one end, travels along fibre, totally internally reflecting

Question 11

What are properties of an image formed when object is beyond 2F?

Answer 11

real
upside down (inverted)
diminished

Question 12

What are properties of an image formed when object is in between F and 2F?

Answer 12

real
upside down (inverted)
magnified

Question 13

What are properties of an image formed when object is in between F and the lens?

Answer 13

virtual
upright
magnified

Question 14

Formula for magnification

Answer 14

img height/object height or /img distance/object distance

Question 15

How is a virtual image formed?

Answer 15

when diverging rays are extrapolated (extended) backwards, not forming a visible screen projection

Question 16

How can short-sightedness be corrected?

Answer 16

adding a diverging lens in front of the cornea

Question 17

How can long-sightedness be corrected?

Answer 17

adding a converging lens in front of the cornea

Question 18

What is the focal length?

Answer 18

distance along principal axis from centre of lens to principal focus

Question 19

What is the focal point/principal focus?

Answer 19

light parallel to principal axis incident on the lens is refracted and meet at the focal point

Question 20

What is the principal axis?

Answer 20

the line that passes through both the centre of the lens surfaces and their centres of curvature

Question 21

What is monochromatic?

Answer 21

visible light of a single frequency

Question 22

order of rainbow (visible spectrum)

Answer 22

ROY G BIV

Question 23

Which colour is refracted the least? Which one the most?

Answer 23

red the least
violet the most

Question 24

What is the speed of red light compared to the others? How does this affect refraction?

Answer 24

faster
refracts less

Question 25

What is the speed of violet light compared to the others? How does this affect refraction?

Answer 25

slower refracts more

Question 26

In glass, what are the relative wavelengths of red and violet light?

Answer 26

wavelength of red is bigger than wavelength of violet

Question 27

State properties of red light.

Answer 27

- faster - refracts less - greater wavelength

Question 28

State properties of violet light.

Answer 28

- slower - refracts more - smaller wavelength

Question 29

State the main regions of the electromagnetic spectrum in order of wavelength, from longer to shorter.

Answer 29

radio waves micro waves infrared visible light ultra violet x rays gamma rays

Question 30

State the main regions of the electromagnetic spectrum in order of frequency, from low to high.

Answer 30

radio waves micro waves infrared visible light ultra violet x rays gamma rays

Question 31

How is the wavelength and the frequency in radio waves?

Answer 31

large wavelength low frequency

Question 32

How is the wavelength and the frequency in gamma rays?

Answer 32

short wavelength high frequency

Question 33

All electromagnetic waves travel at the ______ speed in a vacuum.

Answer 33

same

Question 34

State typical uses of radio waves.

Answer 34

radio and television transmissions astronomy radio frequency identification

Question 35

State typical uses of microwaves.

Answer 35

satellite television mobile phones microwave ovens

Question 36

State typical uses of infrared.

Answer 36

electric grills short range communications (eg TV control remotes) intruder alarms thermal imaging optical fibres

Question 37

State typical uses of visible light.

Answer 37

vision photography illumination

Question 38

State typical uses of ultraviolet.

Answer 38

security marking detecting fake bank notes sterilising water

Question 39

State typical uses of X-rays.

Answer 39

medical scanning security scanners

Question 40

State typical uses of gamma rays.

Answer 40

sterilising food sterilising medical equipment detecting and treating cancer

Question 41

State typical uses of gamma rays.

Answer 41

sterilising food sterilising medical equipment detecting and treating cancer

Question 42

What are harmful effects on people of excessive exposure to microwaves?

Answer 42

internal heating of body cells

Question 43

What are harmful effects on people of excessive exposure to infrared?

Answer 43

skin burns

Question 44

What are harmful effects on people of excessive exposure to ultraviolet?

Answer 44

damage to surface cells and eyes, leading to skin cancer/eye conditions

Question 45

What are harmful effects on people of excessive exposure to X-rays and gamma rays?

Answer 45

mutation or damage to cells in the body

Question 46

What is the speed of electromagnetic waves in a vacuum?

Answer 46

3 x 10ˆ8 m/s

Question 47

What is the speed of electromagnetic waves in air?

Answer 47

approximately same as vacuum

Question 48

What type of electromagnetic radiation is used for communication with artificial satellites?

Answer 48

microwaves

Question 49

What do satellite phones use?

Answer 49

some use low orbit artificial satellites some use geostationary satellites

Question 50

What does direct broadcast satellite television use?

Answer 50

geostationary satellites

Question 51

What are geostationary satellites used for?

Answer 51

some satellite phones direct broadcast satellite television

Question 52

What are low orbit artificial satellites used for?

Answer 52

some satellite phones

Question 53

What do mobile phones and wireless internet use?

Answer 53

microwaves

Question 54

Why are microwaves used for mobile phones and wireless internet?

Answer 54

microwaves can penetrate some walls only require a short aerial (antenna) for transmission and reception

Question 55

What does bluetooth use?

Answer 55

radio waves

Question 56

Why are radio waves used for bluetooth?

Answer 56

radio waves pass through walls (but signal is weakened if this happens)

Question 57

What are uses of optical fibres?

Answer 57

cable television high-speed broadband

Question 58

Why is glass used in optical fibres?

Answer 58

it is transparent to both visible and some infrared light

Question 59

What two waves can carry high rates of data (optical fibre)?

Answer 59

visible light some infrared

Question 60

What is an analogue signal?

Answer 60

signal can be any level within a range and varies continuously

Question 61

What is a digital signal?

Answer 61

signal has fixed values, information is sent in pulses of fixed duration (eg binary)

Question 62

What are benefits of digital signaling?

Answer 62

- increased rate of transmission of data - increased range

Question 63

Why does digital signalling increase range?

Answer 63

because of accurate signal regeneration

Question 64

what is angle of incidence?

Answer 64

angle between normal and ray of light

Question 65

what is angle of reflection?

Answer 65

angle between reflected ray and normal

Question 66

what is refraction

Answer 66

when waves change speed and direction when passing from one medium to another

Question 67

when light travels from a less dense medium to another what happens

Answer 67

it bends towards the normal

Question 68

lens can be

Answer 68

diverging or converging

Question 69

diverging lens (mari ignora)

Answer 69

espalha dps de passar

Question 70

converging lens (mari ignora)

Answer 70

junta dps de passar

Question 71

when top of an image is formed below the optical axis, the image is

Answer 71

inverted

Question 72

when image is formed by extension of light rays, the image is

Answer 72

virtual

Question 73

what is principal focus

Answer 73

point where rays of light travelling parallel to axis meet and converge

Question 74

what is focal length

Answer 74

distance between centre os lens and focal point

Question 75

how is long sight corrected

Answer 75

converging lens

Question 76

how is short sight corrected

Answer 76

diverging lens

Question 77

what is dispersion

Answer 77

splitting of white light through a glass prism into each colour

Question 78

order of colours from longest to shortest wavelength

Answer 78

red orange yellow green blue indigo violet

Question 79

order of colours from shortest to longest frequence

Answer 79

red orange yellow green blue indigo violet

Question 80

what do analogue signals have

Answer 80

continuous electrical signals

Question 81

what do digital signals have

Answer 81

non-continuous electrical signals

Question 82

is sound transmitted as analogue or digital

Answer 82

both :)