physics (3)

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  • Created by: Ellie
  • Created on: 01-06-14 18:40
what is the difference between luminous and non-luminous sources of light?
non-luminous objects do not give off light. You only see them if light bounces off them into your eyes - most objects are non-luminous. Luminous objects give off light.
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Give 2 examples of non-luminous objects
a book and a table
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Give 2 examples of luminous objects
a torch and the sun
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How are shadows formed?
Shadows are formed because light travels in straight lines - light cannot pass through opaque figures, light is blocked by the opaque figures casting shadows on the floor.
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What is the name for when the moon casts a shadow on the Earth?
An eclipse
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what does a small light source produce? what is the given name?
a small light source produces a sharp shadow called an umbra
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what does a large light source produce? what is the given name?
a large light source produces an image with fuzzy edges - it has an umbra and a penumbra
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what is the difference between transparent, translucent and opaque?
transparent objects are see-through; they let light through, translucent objects let light through but break the light up meaning you cannot see through it clearly. Opaque objects don't let light through - you cannot see through opaque objects
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Is light a wave?
yes - similar to infrared
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how does light travel?
in straight lines
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when light hits an object what 3 things can happen? What do these processes mean?
Transmitted - pass through. Reflected - bounce back. Absorbed - stay inside the object
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what happens to an object when it absorbs light energy?
it heats up
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the shorter the light wave the (more/less) energy?
the MORE energy
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name the colours
Red, Orange, Yellow, Green, Blue, Indigo, Violet - ROYGBIV
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what does early morning light in a forest show?
rays of light travelling in straight lines
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what is the definition of reflection?
the change in direction of a light ray after it hits a surface and bounces off
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what does a plane, flat mirror produce?
a virtual image that is behind the mirror and laterally inverted
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describe an experiment to investigate the relationship between the angle of incidence and the angle of reflection at a plane mirror.
shine a light box at a plane mirror, and measure the 2 angles from the normal (an imagionary line draw at right angles from the point where the ray hits). You will find both angles are the same.
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what is the angle of incidence? and the angle of reflection?
angle of incidence = the angle that the ray of light hits the mirror at. angle of reflection = the angle that the ray bounces off the mirror at. Both angles will measure up to be the same
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what is the difference between reflection from a mirror and scattering from a rough surface?
every ray of light hitting the mirror does the same thing so your eyes see a very acurate image of an object (just laterally inverted) - however light reflects off a rough surface in all different directions so you dont see a clear image
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what is the definition of refraction?
the change in direction of a light ray as a result of its change in velocity
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what happens to light when it enters a substance of different density? what determines how much the rays direction will change?
it is refracted - changes direction. The more dense the substance the more the light ray will change direction
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draw a refracted light ray going through a rectangular transparent block
*
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what happens if the angle of incidence is bigger than the critical angle?
the light will be internally reflected (TIR)
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asides from the angle of incidence being bigger than the critical angle - what else cause total internal reflection?
if the light is travelling in a more dense material than the surroundings
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what happens to light when it passes into a substance with a different density?
the light changes direction
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what is the dictionary definition of dispersion?
the splitting up of a ray of light of mixed wave lengths by refraction into its components
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draw a diagram showing dispersion of white light in a triangular prism
*
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why do objects look coloured?
because they reflect that colour but absorb all the rest of the colours in white light. These reflected colour(s) are detected in the back of our eye
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what can be combined to make any colour including white light? name them.
the primary colours: RED, BLUE, and GREEN
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name the secondary colours and what they are made from
Red + Blue = MAGENTA. Blue + Green = CYAN. Green + Red = YELLOW
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why does Ed's tshirt appear yellow?
because it absorbs all the light except yellow which it reflects (Red and Green light)
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what colour will red apples be in green light?
black - because the red apples absorb green light and only reflect red light
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draw ray diagrams to show (a) reflection (B) refraction (C) total internal reflection
*
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how is a prism able to break up white light into its component colours?
the light changes direction and disperses into all the colours of the spectrum
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do all the primary colours have the same wave length?
no - red has a long, spread out with length (with low energy) whereas blue has a short and close together wave length (with high energy)
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what causes light to bend?
light bends when it goes into a denser substance than air and causes the light to slow. Refraction also "bends" light
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the retina of the eye has light-sensitive cells, what are they called? what do each detect?
rods and cones. Rods = dim light and no colour. Cones = bright light and colour
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what does an object appear black?
because it absorbs all of the white light
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Card 2

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Give 2 examples of non-luminous objects

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a book and a table

Card 3

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Give 2 examples of luminous objects

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Preview of the front of card 3

Card 4

Front

How are shadows formed?

Back

Preview of the front of card 4

Card 5

Front

What is the name for when the moon casts a shadow on the Earth?

Back

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