16.A form of progressive wave which has a frequency of 800 Hz and a speed of 350 m s-1 can be stated in the form of the following equation.y = A sin (t - kx).(a) Calculate the value of(i) ,[2 mark](ii) k.[3 marks](b) What is the distance between the two positions which gives the phase difference of rad?[2 marks]17.The diagram below shows two pieces of Polaroids, P and Q, which are arranged such that the polarisation axes make an angle d between one another. A plane unpolarised incident light beam of intensity I0 is applied to Polaroid P. The amplitude of light wave between Polaroids Pand Q is A, and the amplitude after Polaroid Q is

(a) State, in terms of I0, the intensity I1 of the light beam between Polaroids P and Q.[2 mark](b) Calculate the angle between the polarisation axis of Polaroid P and that of Polaroid Q.[3 marks](c) Deduce the intensity I2 of the light beam after Polaroid Q in terms of I0.

[3 marks]

19. (a) Explain how X-ray is diffracted at high intensity in certain directions by a crystal.[3 marks](b) The diagram below shows atoms in a crystal.

The distance a between atoms is 5.63 x 10-10 m. The distance between atomic planes is d.(i) Calculate the value of d.[2 marks](ii) A beam of X-ray with wavelength of range 0.800 x 10-10 m to 1.50 x 10-10 m is directed at a glancing angle of 50.0 to the atomic planes which are shown in the diagram. Determine the wavelengths which are diffracted at high intensity by the atomic planes. [4 marks](c) Radiation emission from a radioactive source is random and spontaneous. Explain what is meant by random and spontaneous.[2 marks](d) The diagram below shows the radiation which is emitted from a radioactive source in a strong uniform magnetic field.

(i) [1 mark] [2marks] [1 mark]Explain why all the lines of radiation P are of nearly the same length.(ii) Explain why the radius of curvature of radiation R varies.(iii) Determine the direction of the magnetic field.