Chapt. 12 Light Flashcards
What is an incident ray?
An incoming ray that strikes the surface
What is a reflected ray?
An outgoing ray that bounces off the surface.
What is a normal?
An imaginary dotted line that is perpendicular to the surface at the point of incidence.
What is a point of reference?
The intersection point on the surface where the incident ray, reflected ray and normal meet.
What is an angle of incidence (i)?
It is the angle between the normal and the incident ray.
What is the angle of reflection (r)?
It is the angle between the normal and reflected ray.
State the 2 Laws of Reflection.
1st: The incident ray, the reflected ray and the normal to the reflecting surface all lie in the same plane.
2nd: The angle of incidence is equal to the angle of reflection.
(i = r)
State the characteristics of a plane mirror.
- Image size = Object size
- Laterally inverted (left-right reversal)
- Upright
- Virtual (cannot be captured on screen)
- Image distance = Object distance
Name 4 applications of mirrors:
1) Optical testing for eyesight: To reduce distance required for optical testing
2) Checking of blind corners: Used in shops to watch out for shoplifters, in vehicles to check for approaching vehicles before making a turn
3) Instrument scales: To avoid parallax error during measurement reading
4) Periscope: To see things across obstacles
What is a refracted ray?
It is an outgoing ray that passes through the surface.
What is an angle of refraction (r)?
It is the angle between the normal and refracted ray.
State the 2 Laws of Refraction.
1st) The incident ray, the refracted ray and the normal to the surface boundary all lie on the same plane.
2nd) For two given media, the ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is a constant. [Snell’s Law]
(sin i/sin r) = constant (refractive index)
Define critical angle (c).
It is defined as the angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90°.
Define total internal reflection.
It is the complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium.
State the conditions for TIR to take place:
1) Light must travel from an optically denser medium to an optically less dense medium.
2) The angle of incidence (i) in the optically denser medium must be greater than the critical angle of the medium (c)
[i>c]
