GEOMETRICAL OPTICS TEST

1. Name the following:
   
   ANSWER
   A = the incident ray, B = the normal at the point of incidence, C = the reflected ray.
   
   
2. What is (a) lateral inversion (b) parallax?
   ANSWER
   (a) Lateral inversion is the reversal of left and right in a plane mirror.
   (b) Parallax is the apparent motion of an object due to the motion of the observer.
   
   
3. State the laws of reflection.
   ANSWER
   Law 1: The incident ray, the normal at the point of incidence and the reflected ray are all in the same plane.
   Law 2: The angle of incidence is equal to the angle of reflection, i = r.
   
   
4. Describe how you would show that light travels in straight lines.
   ANSWER
   
   Get three identical cards. Make a pinhole in the centre of each card.
   Pass a thread through each hole. Pull the thread taut. The three pinholes are now in a straight line. A ray of light will pass through all three holes. If any of the cards are moved out of line, the ray of light will not pass through. This shows that light travels in straight lines.
   
   
5. A person stands 6 m from their image in a plane mirror.
   How far, and in what direction, should they move to be 4 m from the mirror?
   ANSWER
   If they are 6 m from their image, they are 3 m from the mirror.
   If they move 1 m away from the mirror they will be 4 m from the mirror.