Seven colours of Rainbow is produced due — 7 Physics PYQs with Answers | UKPSC PYQ Hub

Question 1

The sun appears/looks Red during sunrise on account of scattering of light Out of the above statements–

Accepted Answer

1 and 3 are correct. Seven colours of Rainbow is produced due to the dispersion of light. Hence, second statement is not correct. When light passes from one medium to another then a part of light is absorbed by particles of the medium, preceded by its subsequent radiation in a particular direction.

Question 2

What is the Standard International Unit (SIU) of measurement of light (Illuminations)?

Accepted Answer

lux. Lux is basically the unit of illumination and is equal to one lumen per square metre. One lux equals 0.0929 foot candles.

Question 3

Due to which of the following, sky appears to be blue ?

Accepted Answer

Scattering. The sky appears to be blue due to scattering of light. Blue light have short wavelength so it scattered more than the other colours in the spectrum, making the blue more visible.

Question 4

In human eye, image of an object forms at

Accepted Answer

Retina. The human eye is like a camera. Its lens system forms an image on a light sensitive screen called retina. Light enters into eye through a thin membrane called the cornea.

Question 5

Which primary colours produce different shades on TV screen?

Accepted Answer

Red, Green and Blue. A monitor or TV screen generates three colors of light (red, green and blue) and the different colors visible on screen is due to different combinations and intensities of these three primary colors.

Question 6

If D and D are the powers of two lenses 1 2 placed in contact, then the power of the combination will be

Accepted Answer

D + D. The power of any two lenses, if 33333 they are placed in contact with each other, will be P = D + D diopters.

Question 7

Which of the following colours of light travels slowest in glass?

Accepted Answer

Violet. The slowest colour to travel through glass in violet. In mediums such as glass, the velocity of light varies depending on its colour (or wavelength). Violet light has the highest refractive index in glass. So, it travels the slowest. In contrast, red light travels the fastest because it has the lowest refractive index.