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Flashcards in Light Deck (35):

Where does light come from?

Light comes from luminous sources


Define luminous

Luminous means that the object emits light


How do we see non-luminous objects?

We see non luminous objects because light is reflected off of them and into our eyes


Describe a convex lens

parallel light will hit the lens and bend across each other
\ /\ ____________


Describe a concave lens

parallel light will hit the lens and bend away from each other
\ \ /
\ \ / ____________


What evidence is there that light travels in straight lines?

1. Shadows
2. The pinhole camera’s image
3. Light streaming through water droplets in clouds
4. Light coming through branches in a forest
5. Light in a laser beam


Name 4 properties of an image in an image from a pinhole camera

The image is ...
1. Inverted
2. Dimmer than the object
3. Smaller than the object
4. Larger the closer it is to the object


How fast does light travel?

300 000 000 m/s


Name and describe the 2 types of shadow

1. Umbra:
•completely black
•no light what so ever

2. Penumbra
•forms when there is a larger or more light sources hitting the shadow
•it’s the outer region of a shadow
•the shadow is dim and fuzzy


Describe a solar eclipse

This happens when the moon is between us and the sun. It’s shadow is cast onto a part of the earth. There is an umbra and penumbra as the sun is larger


Describe a lunar eclipse

This is when the moon moves into the earth’s shadow


What is the ray and angle of incidence?

The incident Ray is where the light comes from
The angle of incidence is how big of an angle from the normal in the Ray


What is the normal?

The normal is an imaginary line 90 degrease to the mirror where we measure angles of rays


What is the ray and angle of reflection ?

The reflection Ray is the light reflected off of a mirror
The angle of reflection is the angle the light is from the normal when it is reflected off of the mirror IT SHOULD BE THE SAME AS THE ANGLE OF INCIDENCE


What is the law of reflection?

The law of reflection is that the angle of incidence and reflection are the same


What are the properties of an image in a plane mirror?

The image is...
•the same size
•Laterly inverted ( reflection | noitcelfer )
The objects in the mirror are..
•the same distance away as the object


What is lateral inversion?

Lateral inversion is when left becomes right and right becomes left


What is refraction?

Refraction is the change in speed of light at a boundary

The light will then bend at the boundary


What is the boundary ?

The boundary is a the line between two transparent densities
E. g.
air to glass
Air to water


What is apparent depth?

Apparent depth is an illusion that our eye dose t know that the light hitting it has been refracted when it comes from the water to the air and so it thinks that the light has originated from a point closer to the surface


What happens when light enters a more optically dense medium?

The light bends towards the normal and slows down


What happens when light leaves a more optically dense medium?

The light bends away from the normal and speeds up


What is the emergent and refraction Ray ?

The emergent Ray is the ray leaving a more optically dense medium
The refraction Ray is the ray that has bent due to it entering a more optically dense medium


What is dispersion?

Dispersion is when light enters a prism and splits up into the spectrum of colours that make white light


What is the order of colours in dispersion?

Red, Orange, Yellow, Green, Blue, Indigo, Violet


How does dispersion occur?

Dispersion occurs because the different colours that make white light is refracted by different amounts as they enter and leave the glass.


What is the change of light’s direction called?



What is it called when light splits up into many colours?



How are colours made?

Colours are made by mixing other colours of light.


What are the 3 primary colours of light

Red, Green, Blue


What are the 3 secondary colours and what colours are mixed to make them?

Magenta(purple/pink) = Red + Blue
Cyan(light blue) = Blue + Green
Yellow = Red + Green


How do we see certain primary colours. Eg Red

All the colours except the colour we are seeing (red) is absorbed by the object


How do we see certain secondary colours? Eg Magenta

The object absorbs all colour except red and blue, mixing the two colour and making magenta


How do we see black?

The object absorbs all of the colours, therefore we don’t have any light reflecting off of it.


How Do we see white?

All colours are reflected off of the object making us see all of the light.