13.
Through a soap film, different colours are seen by white light because of the phenomenon of
Answer : A. Interference
14.
A decibel is
Answer : A. the relative intensity of sound
15.
Optical fibre works on the principle of
Answer : A. total internal reflection
16.
The colour of an opaque object is due to the colour it
Answer : C. reflects
17.
Reed instrument without pipe is
Answer : B. Harmonium
18.
Arrange the following colours in increasing order of wavelength i) orange ii) indigo iii) yellow iv) violet
Answer : C. iv,ii,iii,i
