Methods to polarise light:
(i) Light can be polarised by shiny transparent materials.
(ii) Light can be polarised when it falls on a non-metallic surface.
(iii) When light scatter by small particles e.g., air molecules, it is polarised.
An astronomical telescope consists of two convex lenses having focal length 80 cm and 4 cm. When it is in normal adjustment, what is its:
(i) Length,
(ii) Magnifying power?
(i) Define ‘unified atomic mass unit’.
(ii) Find the minimum energy which a gamma ray photon should possess so that it is capable of producing an electron — positron pair.