Chapter 5 - Optics Flashcards
What is refraction?
The change of direction that occurs when light passes at an angle across a boundary between two transparent substances.
Which way does light bend?
Toward the normal when passing into a more dense substance, and away from the normal when passing into a less dense substance.
What happens if incident light is along the normal?
Light is not refracted.
What is Snell’s law?
The ratio of sin(i)/sin(r) is always constant for each light ray, where i is the angle of incidence and r is the angle of refraction.
What is the refractive index?
n = sin(i)/sin(r) = c/cₛ
Partial reflection also occurs when a light ray in air enters a refractive substance.
Partial reflection also occurs when a light ray in air enters a refractive substance.
n = speed of light in a vacuum/speed of light in the transparent substance
n = speed of light in a vacuum/speed of light in the transparent substance
What is the critical angle?
The angle at which the light ray rafracts along the boundary. sin(feta) = n1/n2
What is total internal reflection?
When the angle of incidince is greater than the critical angle, resulting in the light ray being fully reflected.
What are the conditions for total internal reflection?
If the incident substance has a larger refractive index, and if the angle of incidence is greater than the critical angle.
Why may optical fibres be used?
Light rays are totally internally reflected in optical fibres due to the greater refractive index of the core.
Why are the slits in Young’s double slit experiment coherent?
So they can emit waves with constant phase difference and with the same frequency.
Why are fringes formed?
Due to the interference of light. A bright fringe is formed where the light from each slit arrives in phase, whereas the dark slits are formed where the light from each slit arrive 180* out of phase.
Fringe separation, w = λD/s (where λ is the wavelength, D is the distance from slits to screen, s is the slit spacing).
Fringe separation, w = λD/s (where λ is the wavelength, D is the distance from slits to screen, s is the slit spacing).
