Light Flashcards
State the 1st Law of reflection
The angle of reflection is equal to the angle of incidence.
State the 2nd Law of reflection
The incident ray, the reflected ray and the normal the point of incidence all lie on the same plane.
Define Angle of incidence
The angle between the incident ray and the normal.
Define Angle of reflection
The angle between the reflected ray and the normal.
Define Normal
the line that is perpendicular to the reflecting surface or boundary between 2 media.
Characteristics of image formed by plane mirror (5 characteristic)
- Same size as object
- Laterally inverted
- Upright
- Virtual
- The distance of the image from the mirror = distance of object from the mirror
Define Angle of refraction
The angle between the refracted ray and the normal.
State the 1st Law of Refraction
For 2 given media, the ratio of sini/sinr is a constant, where i is the angle of incidence and r is the angle of refraction.
Note: i must be in the optically less dense medium.
State the 2nd Law of Refraction
The incident ray, the refracted ray and the normal at the point of incidence all lie on the same plane.
Explain what is meant by the refractive index of a medium
The refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light in that medium.
What are the formula for calculating refractive index (3 formulas)?
1) n=sini/sinr (Note: i must be in the optically less dense medium)
2) n= real depth/apparent depth
3) n= speed of light in vacuum/speed of light in medium = c/v
Define critical angle
It’s the angle of incidence in the optically denser medium for which the angle of refraction in the optically less dense medium is 90 degrees.
Formula for critical angle
n= 1/sinc
State the 2 conditions for total internal reflection to occur.
- The light is travelling from an optically denser to an optically less dense medium
- The angle of incidence is greater than the critical angle
Define focal length
The distance between its optical centre and principal focus (or focal point)
