IGCSE Physics (0625) 3.2.4 Dispersion of light Paper 4

Question

(a) In Fig. 6.1, a ray of red light is shown passing through a triangular glass prism and on to

another prism that is identical but upside down.

(a) The angle of incidence of the red light at the first surface is shown on Fig. 6.1 as i.

On Fig. 6.1, use the letter r to mark clearly the angle of refraction at the first surface.[1]

(ii) On Fig. 6.1, complete the path of the ray through the right-hand prism and out

into the air again. Label the emergent ray “line R”.                                                             [3]

(iii) The beam of red light is moved so that it shines into the right-hand prism along line R.

Using the letter P, mark clearly the point where this ray will emerge from the left- hand prism. [1]

(b) On another occasion, a beam containing a mixture of red and blue light is shone into a prism, as shown in Fig. 6.2.

1. 1. On Fig. 6.2, draw the path of the blue light through the prism and out into the air again. [3]

   2. Refraction is occurring at the first surface.

                                                                              [1]                            [Total: 9]

      Answer/Explanation

      Ans: (a) (i) r correctly shown 

      (ii) bent up at first surface  bent up at second surface  straight line within prism
      (iii) P clearly shown as the original point of entry

      (b) (i) blue light refracted from same point at first surface  blue shown with greater refraction  blue light always below red light 

      (ii) dispersion