1. Why fluorescent tube light is considered better than tungsten filament-bulb?
The luminous efficiency of tungsten filament lamp is ~ 3 % while that of fluorescent tube light is nearly 9 %. Therefore the tube light gives 3 times more luminously than a filament bulb for same consumption of electric power.
2. Why there is summer in December and Winter in June in Southern hemisphere?
In Southern hemisphere the angle of incidence of sun rays is minimum in December and maximum in June. Hence there is summer in December and winter in June.
3. Why a photographer uses a red bulb in his dark room?
In visible light the red colour has maximum wavelength and minimum energy. Therefore red light does not affect the photographic film.