Write the value of the near point of distinct vision for a normal eye.

What are hypermetropia and myopia? What are their causes? How are they rectified?

In the figure,a ray of light $PQ$ is incident normally on one face $AB$ of an equilateral glass prism. What are the angles of incidence at faces $AB$ and $AC$?

What is long-sightedness (hypermetropia)?

Through which part of the eye do light rays from an object first enter the eye?

$A$ 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?