(a) The sun outputs about 1300 watts per square meter (W∕m2) in space near the earth, which gets reduced to around 650W∕m2 after through the atmosphere. So, the amount of heat is quite realisable.
The forces generated by solar radiation is generally too small to be noticed under everyday life. The radiation pressure of sunlight on earth is equivalent to that exerted by about a thousandth of a gram on an area of 1 square metre. It is approximately 10µN∕ m2. Hence, it is negligible.
(b) Wavelength and velocity of electromagnetic wave change from one medium to another medium.
(c) Ozone layer absorbs biologically harmful ultraviolet radiation coming from the sun. Hence, it is crucial for humans' survival on earth.