P14- Light Flashcards
Law of reflection in a mirror
3 parts?
1 key fact?
-Line perpendicular to the mirror is called the normal
-Angle of incidence is between initial ray and the normal
-Angle of reflection is between reflected ray and the normal
Angle of incidence= angle of reflection
Virtual image
Inversion?
Where is it formed?
Same way up as the object, but laterally inverted
The place where light rays appear to come from before being reflected
Specular reflection
Diffuse reflection
Smooth, flat surface, doesn’t scatter light, creates a virtual image
Rough surface, light scattered in dif directions
Refraction
Change in direction of a wave when crossing a boundary between one medium and another
Why do light waves refract through an object?
Due to the change in speed of light
Where does light refract in a more dense medium than air?
and a less dense medium?
More dense = refracted towards the normal
Less dense = refracted away from the normal
Light travelling from air into glass affecting..
Direction?
Angle of refraction?
Angle of incidence?
Travels from air into glass, direction towards the normal, angle of refraction is smaller than angle of incidence
Light travelling from glass into air affecting..
Direction?
Angle of refraction?
Angle of incidence?
Travels from glass into air, direction away from the normal, angle of refraction is greater than angle of incidence
How to investigate the refraction of light?
-Use a slit in a ray box to create a thin ray of light
-Place first material on paper, trace around it
-Draw a ‘normal’ which is perpendicular to one side of the box drawn
-Point the light ray where the normal meets the block, this is the incidence ray
-Draw the reflected and the refracted ray, then join the point of reflection and the refracted ray together
-Use protractor to measure the angle of incidence, angle of reflection and angle of refraction
-Repeat with different angles of incidence, then with different materials
-Don’t touch the ray box as it heats up!
What are the primary colours of light?
What are the secondary colours of light?
Red, green, blue
Magenta, yellow, cyan
What colours are needed to make the secondary colours?
Blue and red= magenta
Red and green= yellow
Blue and green= cyan
What colours of light are reflected in a white, black, red and blue object?
White= all wavelengths of light
Black= no wavelengths of light (are absorbed)
Red= red light
Blue= blue light
Transparent object affecting light?
Transmits all light incident on it, light travels through object
Translucent object affecting light?
Light is scattered or refracted due to internal boundaries, light passes through but can’t see images
Opaque object affeting light?
Absorbs all light incident on it, no light passes through
What does the colour of a surface depend on?
The pigments it contains and which wavelengths of light they absorb
Why does are there different colours of light?
There are different wavelengths of light
Colour of light with the smallest and largest wavelength?
Colour of light with smallest and largest frequency?
Smallest wavelength= violet
Largest wavelength= red
Smallest frequency= red
Largest frequency= violet
Convex lens
Aka?
Causes rays to..?
Focal point is?
Used for?
Converging lens
Converge to a focus
Point where rays are focused
Magnifying glass, camera
Concave lens
Aka?
Causes rays to..?
Focal point is?
Used for?
Diverging lens
Diverge
Point where the rays appear to come from
Correct short sight
Focal length?
How does it affect the lens strength?
Distance between centre of lens to principal focus
Smaller focal length, stronger lens
How many focal points do lenses have and where?
What do they allow?
Two, one on each side
Allows the lens to be used both ways if light travels from other side
Principal axis?
Imaginary line through the lens
Magnification equation
Image height / object height = magnification
What type of image is formed from an…
Object more than twice the focal distance from convex lens?
-Smaller
-Real
-Inverted
What type of image is formed from an…
Object between one and two focal distances from convex lens?
-Bigger
-Real
-Inverted
What type of image is formed from an…
Object less than the focal distance from convex lens?
-Bigger
-Virtual
-Upright
What images do concave lenses produce?
-Smaller
-Virtual
-Inverted
2 things that change the position and nature of an image?
-Focal length of lens
-Distance of object from lens
Symbol for convex lens?
Symbol for concave lens?
