Topic Menu

Cyber-chess a chess instruction site

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.

concave  
convex
diverging  

 

(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

An answer of 0.05 gains 1 mark - you should know that focal lengths must be expressed in metres before the power of the lens in dioptre can be calculated.

(3 marks)

 

(Total 11 marks)