The focal length of the eye lens can be changed due to the action of $......................$.

Cinematography makes use of

$A$ student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw a ray diagram for the correction of this defect.

Study the diagram given below and answer the questions that follow it.
$(i)$ Identify the defect of vision represented in this case. Give a reason for your answer.
$(ii)$ Mention the two causes of this defect.

$A$ human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

The far point of a myopic person is $40 \, cm$. What type of lens should they wear to see distant objects clearly? Calculate the focal length and the power of the lens they should use.