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Physics > Chapter 7 - Light > Flashcards

Chapter 7 - Light Flashcards

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1
Q

What are the properties of reflection

A

All types of waves can be reflected

The velocity, freequency, and wavelength of the reflected and incident ray are the same

Waves are in the same medium

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2
Q

What is the principle of reflection

A

Angle of incidence = angle of reflection

Incident ray, reflect ray, and normal lie in the same plain.

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3
Q

What happens if the gap is bigger in diffraction

A

The bending effect reduces

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4
Q

What is the normal

A

A fictious line that is perpendicular to the plain surface.

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5
Q

What are the 3 types of surfaces to reflect on
how much reflection

A

Rough/curved - diffused reflection
smooth - almost all light is reflected, some is transmitted
Mirror - 100% of the light is transmitted

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6
Q

How does the wave refract thru diff mediums

A

Rarer to denser - Towards the normal
Denser to rarer - away from the normal

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7
Q

Refractive index formula

speed of light

A

Speed of light in m1/speed of light in m2

m1 and m2 = medium 1 and medium 2

or

c/v

c = speed of light in vaccum = 3 * 10^8 m/s
v = speed of light in medium 2

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8
Q

What is a spectrum
why is a spectrum formed when light passes through a prism

A

a range of colours

Dispersion

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9
Q

Properties of a virtual image

A

Laterally inverted
Distance of object and image from the mirror are the same
Size of object and image are the same
Upright image
Cannot be caught on a screen

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10
Q

What wave fronts do diff light sources give
name the light sources

A

Extended light source - cylindrical wave fronts
Point light source - spherical wave fronts.

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11
Q

what is a critical angle

A

angle at which refracted ray is parallel to the surface of material.

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12
Q

what is a principal focus

A

Principal focus: the point where rays parallel to the principal axis converge with a converging lens.

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13
Q

what is the principal axis

A

line that goes through optical center, and the 2 foci.

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14
Q

what is the optical centre

A

the center of the lens

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15
Q

what is the focal length

A

distance from principle focus and the optical centre.

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16
Q

when is a real image formed

A

When object is behind F1

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17
Q

when is a virtual image formed

A

when object is ahead of F1

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18
Q

define refraction of light

A

Refraction is the bending when light travels from one medium to another due to the change in speed of the ray of light.

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19
Q

what do convex lenses to do light rays

A

they converge them

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20
Q

properties of images formed in convex lenses

A

The image is upright and magnified, it is a virtual image.

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21
Q

how does dispersion of light occur

A

If a beam of white light is passed through a prism it is dispersed into a spectrum.

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22
Q

what is monochromatic light

A

Monochromatic light is that of a single frequency.

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23
Q

Common features of EM waves

A

travel through vacuum

travel at the speed of light

are transverse waves

transfer energy

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24
Q

When are EM waves emited

A

emitted whenever charged particles oscillate or lose energy

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25
Q

Electromagnetic spectrum (organized by increasing wavelength)

A

Gamma
x-rays
ultraviolet
light
infrared
microwaves
radio waves:
UHF, VHF, short waves, medium waves, long waves

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26
Q

what are VHF and UHF waves

A

VHF - very high frequency

UHF - ultra high frequency

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27
Q

Infrared radiation and light
how does an object glow when its heated and at what temp

A

All objects emit some infrared radiation

When an object heats up, it emits more and more infrared and shorter wave lengths.

at 700 degrees - produces shortest possible wavelengths that can be detected- glows red hot

at 1000 - entire spectrum is covered and the object glows white hot

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28
Q

What is flouresense

A

Materials that absorb ultra violet and convert its energy to visible light and glow.

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29
Q

What are x-rays

their penetration powers

A

Rays that are given off when fast-moving electron lose energy very quickly.

short wavelength x rays are extremely penetrating
long wavelength x rays are less penetrating

30
Q

gamma rays

where do they come from
when are they produced

A

Rays that come from radioactive materials. Produced when the nuclei of unstable atoms break up or lose energy.

31
Q

properties of image that originate from behind 2f1

A

Real
Inverted
Diminished (smaller than the object)

32
Q

Properties of image that originate between 2f1 and f1

A

Real
inverted
enlarged (larger than the object)

33
Q

What happens when the object is in between the f1 and the lens

A

Rays never converge - form a virtual, upright and magnified image
cannot be caught on a screen

34
Q

Properties of images formed by concave lens

A

Virtual
Upright
Smaller than object

35
Q

what happens when the angle of incidence is less than the critical angle

A

partial reflection, some light is refracted and some light is reflected

36
Q

what happens when the angle of incidence is greater than the critical angle

A

total internal reflection occurs

37
Q

what happens when the angle of incidence is equal to the critical angle

A

the angle of refraction is 90 degrees and the refracted ray lies on the principal axis

38
Q

what physics property do optical fibers make use of

what is their medical use of optical fibres
where else are they used

A

total internal reflection - all rays are reflected no ray is refracted and escaped

medical use: surgery (endoscopy)
other use: telecommunication

39
Q

what is the speed of light

A

3x10^8 m/s

40
Q

name all the types of waves in order in the electromagnetic spectrum

A

radio waves
microwaves
infrared waves
visible light
ultraviolet
x-ray
gamma ray

41
Q

which are the broad electromagnetic rays

A

radio rays
light rays
gamma rays

42
Q

as we go from gamma to radio waves what increases/decreases

A

wavelength increases from gamma to radio (radio has highest wavelength)
energy decreases from gamma to radio (gamma has highest energy)
frequency decreases from gamma to radio (gamma has highest freq)

43
Q

what are all the colours in the visible light spectrum (give acronym)

A

violet
indigo
blue
green
yellow
orange
red
(VIBGYOR)

44
Q

as we go from violet to red how does the wavelength, speed and frequency change

A

wavelength increases (red has highest wavelength)
frequency decreases (violet has highest frequency)
speed increases (red has highest speed)

45
Q

which waves travel at the same high speed in a vaccum

A

infra-red waves, microwaves and radio waves

46
Q

which waves are used to transport television pictures from satellites

A

microwaves

47
Q

when drawing reflection images what is important

A

draw a bisector of the reflected and incident ray
make sure the angle between incident and bisector = reflected and bisector

48
Q

refractive index formula, critical angle

A

refractive index = 1/sin critical angle

49
Q

Describe the harmful effects on people of excessive exposure to electromagnetic radiation

microwaves
infrared
ultraviolet
x rays
gamma rays

A

microwaves; internal heating of body cells
infrared; skin burns
ultraviolet; damage to surface cells and eyes, leading to skin cancer and eye conditions
X-rays and gamma rays; mutation or damage to cells in the body

50
Q

Define total internal deflection

A

Reflection in a more dense material where there is no refracted ray

51
Q

Describe how optical fibres are used in telecom

A

Carry telephone calls and internet data

Signals are coded and sent along the fibre as pulses of laser light

52
Q

What happens in a short sighted

solution

A

Incoming rays bend inwards too much before they reach the retina

solution: A concave lens placed in front of the eye

(look at diagram on page 157 of tb atl once to get a good idea)

scientific name - myopia

53
Q

What happens in a long sighted eye

solution

A

Incoming rays don’t bend inwards enough so when they reach the retina they still haven’t met

solution: a convex lens in placed in front of the eye

(look at diagram on page 157 of tb atl once to get a good idea)

hyperopia

54
Q

What is a bifocal lens

A

Top of the lens aid in looking at distant objects

bottom part of the lens - looking at objects that are close

55
Q

In order to use a convex lens as a magnifying class, where does the object have to be

what kind of image
properties of image
where is the eye

A

Object between F1 and Lens

Virtual image
Upright
magnified
Cannot be picked up on a screen

Eye - opposite side of the object looking through the diverging rays

56
Q

Common uses of radio waves

A

radio and television transmissions

astronomy

radio frequency identification (RFID) - Contactless debit and credit cards contain a tiny chip. When a reader sends out radio waves the chip emits data signals.

57
Q

Common uses of microwaves

A

satellite television
mobile phones
microwave ovens

58
Q

Common uses of infrared waves

A

electric grills
short range communications such as remote controllers for televisions
intruder alarms
thermal imaging
optical fibres

59
Q

Common uses of visible light

A

vision
photography
illumination

60
Q

Common uses of UV

A

security marking
detecting fake bank notes
sterilising water

61
Q

Common uses of Xray

A

medical scanning
security scanners

62
Q

Common uses of gamma

A

sterilising food and medical
equipment

detection of cancer and its
treatment - cheomotherapy

63
Q

How is communication between satelites possible

types of satellite phones

A

Microwaves

some satellite phones use low earth orbit (LEO) artificial satellites

some satellite phones and direct broadcast satellite television use geostationary (GEO) satellites

64
Q

Why do mobile phones and wireless internet use microwaves

A

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

65
Q

How does Bluetooth make use of EM waves

why? disadv

A

low energy radio waves or microwaves

they can pass through walls but the signal is weakened on doing so

66
Q

Which em waves are used in optical fibres

A

visible light
infrared rays

67
Q

Define an analogue signal

define a digital signal

A

Sound waves entering a microphone make its voltage across vary. When this variation is continous it is known as an analogue signal

Digital signal - a signal represented by numbers

68
Q

2 ways sound can be transmitted

A

as a digital or analogue signal

69
Q

benefits of digital signaling

A

including increased rate of transmission of data

increased range due to accurate signal regeneration

70
Q

describe one use of optical fibre in medicine

A

Light travels down (optic) fibres into or out of body
To examine internal organ
Light travels both ways into and out of body

Physics (25 decks)

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