P14 Flashcards
What does a lens do
A lens forms an image by refracting light
What happens in a convex lens
parallel rays of light are brought to a focus at the principal focus. The distance from the lens to the principal focus is called the focal length
What is the focal length
The distance from the lens to the principal focus
What are the images produced by convex and concave lenses
The image produced by a convex lens can be either real or virtual.
The image produced by a concave lens is always virtual.
How to calculate the magnification produced by a lens
magnification = image height/ object height
How are convex and concave lenses shown in ray diagrams
↕️ - convex
🔽
| - concave
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What is a colour in terms of light
Each colour within the visible light spectrum has its own narrow band of wavelength and frequency.
What reflection from a smooth surface called
Reflection from a smooth surface in a single direction is called specular reflection
What is reflection from a rough surface called
Reflection from a rough surface causes scattering: this is called diffuse reflection.
How do colour filters work
Colour filters work by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).
How is colour seen on an opaque object
The colour of an opaque object is determined by which wavelengths of light are more strongly reflected. Wavelengths that are not reflected are absorbed. If all wavelengths are reflected equally the object appears white. If all wavelengths are absorbed the objects appears black.
How to draw a ray diagram for a convex lens
Draw a line parallel from object to the lens and connect it to the principal focu on the other side of the lens
Draw a line passing through the middle of the lens
Where the two lines meet it the top of the image
Optional: draw a line passing through the first principal focus until it reaches the lens and make it go parallel
How to draw a ray diagram through a concave lens
Draw a parallel line which stops at the lens and then draw a line going way from the second principal focus until it is in line with it
Then draw a line from the top of the object which passes through the middle of the lens
Then draw a from the refracted ray going outwards, back towards the first principal focus and where this line crosses the line cutting the middle is the top of the image
How to draw a ray diagram for a magnifying glass ( principal focus behind object )
Draw a line parallel from the object to the lens
Draw a line that passes through both the second principal focus and where the parallel line meets the lens
Draw a line going through the top of the object and the middle of the lens
Where the 2nd and 3rd line meet is the top of the image
