GCSE level optics questions
Q15.
(a) The diagram shows light rays entering and passing through a lens.
(i) Tick in the table below the type of lens is that is shown in the diagram.
(ii) State the name given to point X in the diagram.
The focal point or principle focus of the lens
(2 marks)
(b) A lens acts like a number of prisms.
The diagram below shows two parallel rays of light entering and passing through prism A and prism C.
Draw a third parallel ray entering and passing through prism B.
(4 marks)
(c) Name two factors that determine the focal length of a lens.
refractive index (optical density) of the material it is made from
radius of curvature of the lens
(2 marks)
(d) A converging lens has a focal length of 20 cm.
Calculate the power, in dioptre, of the lens.
Power (in dioptres) = 1/focal length (in metres)
f = 0.20 m
P = 1/0.20
P = 5 D
(3 marks)
(Total 11 marks)