Refraction and Converging Lenses Flashcards
What affects the speed of a wave
The density of the substance or medium it’s travelling in
What is the formula for wave speed?
Wave speed = frequency x wavelength
How do converging lenses use refraction to focus light waves?
Because they are curved, the light ray hits the surface and slows down as it passes from air to glass. This cause the ligth ray to bend towards the ‘normal’. The curvature of the lens means all the parallel rays hitting different parts of the lens are bent towards the same focal point, where an image is formed.
What is the ‘normal’?
The line at right angles to the boundary at the point where the ray enters or leaves
What factor determines how much a light ray is refracted?
Different wavelengths
Why does white light emerge how it entered into a rectangular prism?
Because it has parallel boundaries so the rays bend one way as they enter and then bend back again by the same amount as they leave
What is a principal axis?
A line which passes straight through the middle of the lens
What is the focal point?
Where the rays initially parallel to the principal axis meet
What is the focal length?
The distance between the middle of the lens and the focal point
What is the formula for the power of a lens?
Power (D) = 1 / Focal Length (m)
How would you make a more powerful lens from the same material?
Just make it with a more strongly curved surface
