P14: Light Flashcards
How do lenses form images?
By refracting light
What happens in convex lenses?
Parallel rays of light are brought to a focus at the principle focus.
What is the focal length?
The distance from the lens to the principle focus
What kind of image is produced by a convex lens?
Real or virtual
What kind of image is produced by a concave lens?
Always virtual
What is specular reflection?
Reflection from a smooth surface in a single direction
What is diffuse reflection?
Reflection from a rough surface, causing scattering
How do colour filters work?
By absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour)
When is an object white?
When all wavelengths are reflected equally
When is an object black?
When all wavelengths are absorbed equally
Which colour has the longest wavelength?
Red
Which colour has the shortest wavelength?
Violet
What does the colour an object appear to be depend on?
The wavelength of light hitting it and the property of the object
What are opaque objects?
Those that don’t transmit any light
What 2 colours should be reflected to form yellow?
Red and green
What are transparent objects?
Those that transmit most light, with a small amount being absorbed
What is another name for a convex lens?
Converging lens
What does a converging lens do?
It refracts parallel rays of light inwards to a single point (principle focus)
What does it mean if the focal length is short?
The lens is more powerful as it refracts light more strongly
How would you make a lens more powerful?
Use a different material or make the lens more curved
What is the difference between a real image and an imaginary image?
Real image is formed when rays cross but virtual image is where virtual rays cross. Virtual image is where rays seem to come from
