Q1 A student carried out an experiment to measure the wavelength of monochromatic light by allowing a narrow beam of the light to fall normally on a diffraction grating with 400 lines per millimetre.The student ultimately ended up with the following data.
Table 14.3 n / degrees 1 13.6 2 28.1 3 45.0
(i) Describe, with the aid of a labelled diagram, how the data was obtained. (ii) Use all the data to calculate a value for the wavelength of the light.
(iii) What is the maximum number of bright images that could be observed using that light’s source and grating?
(15) (15)
(10)
‘SECTION B’ SHORT QUESTION
Typical of Question 5 in Leaving Cert. Exam Q2 Answer all of the following parts (a), (b), (c), etc.
(a) In the seventeenth century there were two conflicting theories about the nature of light. What were they?
(b) What contribution did Thomas Young make to physics in the early part of the nineteenth century? (c) What is the grating constant of a diffraction grating with 800 lines per millimetre?
(d) The first order image of a monochromatic light source is at an angle 21 to the zero order image. The grating constant, d, is 2.0 10–6 m.What is the wavelength of that light?
(e) Give one use of a spectrometer.
(f) Give two properties which are common to all electromagnetic radiations. (g) Which one of the following is not part of the electromagnetic spectrum? sound waves microwaves gamma radiation
(h) What contribution did James Clerk Maxwell make to physics in the nineteenth century?
(i) Dispersion can be demonstrated using a prism or a diffraction grating. Give one difference in the spectrum of colours produced by the different methods.
