Unit 3 - Lenses Flashcards
What is refraction
When a ray of light crosses the boundry between two different transparent materials and it changes direction
What does it mean hen something has deviated?
It has changed direction
When light goes from air into a denser material, does it go towards or away from the normal? (when the wave slows down)
Towards
What is the ray called that goes into the material?
The incident ray
What is the ray of light called that has changed direction and is inside the material?
The refracted ray
What is the ray of light called that goes out of the material?
The emergent ray
When a ray of light goes from a denser material to an less dense material, does it go towards or away from the normal?
Away from
What is the reason for the change in direction during refraction?
The change in speed
At what angle is light not refracted?
90°
What is the angle of incidence
The angle at which the ray of light hits the medium
What the the refractive index fo a material?
the ratio of speed of light in a vacuum to speed of light in that medium
What is the equation for the refractive index?
Refractive index = sin i / sin r
- I to the sky (outside the shape)
- R will always be smaller than r
When given the angles of incidence/refraction, how do you encorperate this into the equation for the refractive index?
Do sin of the angle, and then use this in the actual equation (aka sin i / sin r)
eg I = 42° R=35°
sin i = sin(42)=0.67 and sin r = sin(35) = 0.57
So RI = 0.67/0.57 = answer
The refractive index will always be..?
More than 1
When working out the angle of refraction, what is the equation?
Sin i / n = sin r
→ Sin-1(ans) = answer
How do lenses form images?
By refracting lights and changing its direction
What are the two main types of lenses?
Converging and diverging
Is a converging lense convex or concave?
Convex
What is a convex lense and hat does it do?
A lense that buldges outwards and causes parallel rays of light to converge (move together) at the pricipal focus
Is a diverging lenses convex or concave?
Concave
What shape is a concave length? and what does it do
It caves inwards, it causes parallel rays to diverge (spread out)
What is the axis of a lens?
A line passing through the middle of the lens
What is the principal focus.focal point of a converging lens?
Where rays hitting the lens parallel to the axis all meet
What is the principal focus/focal point of a diverging lens?
The point where rays hitting the lens parallel to the axis appear
What is the focal length
The distance from the centre of the lens to the principal focus/focal point
