reflection and diffraction Flashcards

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1
Q

what is the law of reflection

A

the fact that the angle of incidence equals the angle of reflection

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2
Q

what is the angle of incidence

A

the angle between the normal and incident Ray

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3
Q

what is the angle of reflection

A

the angle between the reflected Ray and the normal

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4
Q

what is the normal

A

the imaginary line drawn at 90* to the reflecting surface

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5
Q

describe a reflected image

A

a reflected image is

virtual
right way up
and same size

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6
Q

what are the best surfaces to reflect

A

smooth surfaces produce strong echos when sound wave hit them and act as a mirror when light waves hit them. the waves are reflected uniformly (evenly) and can form images

rough surfaces scatter sound and light in all directions

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7
Q

what can waves do in terms of reflection

A

they can be focuses to a point

they can appear to come from a point behind a mirror

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8
Q

what is refraction

A

the change of direction of a light rat when it passes across a boundary between 2 dsubstances with different densities

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9
Q

what do sound waves and light waves do in refraction

A

they change speed which causes them to change direction

but they bend back to the original direction once it leaves the block

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10
Q

when wont refraction happen

A

reaction doesn’t happen if the waves cross the boundary at an angle of 90* (they carry straight on)

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11
Q

what happens to the angle of refraction as u increase the angle of incidence

A

as you increase the angle of incidence you see a greater angle of refraction

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12
Q

what is the critical angle

A

at a specific angle (42*) cannot refract any longer and just goes down the side of the block

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13
Q

why does the light refract or bends towards the normal

A

light refracts or bends towards the normal because it slows down as it enters the glass

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14
Q

why does light reflect and bend away from the normal

A

the light reflect and bend away from the normal because it speeds up as it goes from glass to air

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15
Q

what happens when white light passes through a triangular prism

A

as it leaves the prison the different wavelengths of the individual xolours of light result in different angles of refraction

this splits the White light into the 7 colours of the rainbow this process is called dispersion. each colour of light can be called monochromatic

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16
Q

is the angle of reflection bigger or smaller than the incidence angle

A

the angle of refraction is bigger than the incidence angle

17
Q

why is the angle of refraction bigger than the angle of incidence

A

because when the light moves from a substance to another substance where it moves faster it refracts and bends away from the normal

18
Q

what happens is the angle of incidence gets bigger than the critical angle

A

it doesn’t refract

instead it totally internally reflects

19
Q

what is an optical fibre

A

thin glass fibre used to send light signals along

uses totally internal reflection

20
Q

where do sound and light waves reflect reflect from

A

from surfaces

21
Q

what is diffraction

A

diffraction is the spreading out of waves when they pass through a gap round the edge of an obstacle