State the function of the pupil and ciliary muscles.

$A$ beam of white light falling on a glass prism gets split up into seven colours marked $1$ to $7$ as shown in the diagram. $A$ student makes the following statements about the spectrum observed on the screen.
$(a)$ The colours at position marked $3$ and $5$ are similar to the colour of the core of a hard-boiled egg and the colour of the sky respectively. Is the statement made by the student correct or incorrect? Justify.
$(b)$ Which of the two positions correspond closely to the colour of $(i)$ a solution of potassium permanganate,$(ii)$ danger or stop signal lights?

Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence,define the angle of deviation.

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

How are we able to see nearby and also the distant objects clearly?

The brilliance of a diamond is due to which phenomenon?