C
CraftExam
high importancemedium difficulty6 min

Myopia

Myopia is a defect in which a person sees nearby objects clearly but distant objects appear blurred.

In one line: Myopia means near clear, far blurred.

Practice This Concept

Understand it

In myopia, light from a distant object is focused in front of the retina instead of on it. This can happen because the eyeball is too long or the eye lens has too much converging power. A concave lens is used for correction because it spreads the rays slightly before they enter the eye.

Example

A student can read a book easily but cannot clearly see the school notice board from the back row.

Formula and rule

Myopia correction uses a concave lens of suitable focal length to reduce the eye's converging power.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

  1. 1If a student cannot see objects beyond 2 m clearly, the far point of the eye is 2 m.
  2. 2A concave lens is chosen so distant rays are diverged and the final image forms on the retina.

Method you can reuse

  1. 1State that nearby objects are clear but distant objects are blurred.
  2. 2Mention that the image forms in front of the retina.
  3. 3Give possible cause: long eyeball or excessive lens power.
  4. 4Say that a concave lens is used.
  5. 5Explain that the lens diverges rays so the image moves to the retina.

Sketch it in your answer

Draw a myopic eye with parallel rays focusing before the retina, and then show a concave lens making the rays diverge before entering the eye.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is a concave lens used to correct myopia in a student?

Think first, then show answer
A concave lens is used because it diverges incoming light rays slightly, so the image of a distant object is shifted back onto the retina. That helps the myopic eye see far objects clearly.

Common wrong answer

A common wrong answer is to choose a convex lens.

Why it loses marks: A convex lens would increase convergence and make the distant image form even earlier.

Don't mix this up

Students often say myopia means 'short sightedness' but forget to mention that the image of distant objects forms in front of the retina.

Exam tip

In correction answers, mention concave lens, diverging rays, and image shifting to the retina.

Myopia diagram

Open full screen to read every label clearly.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Explain the defect, identify the lens used for correction, or draw a ray diagram showing the corrected image position.
  1. 1

    Enough for 1 mark

    Myopia is a defect in which a person sees nearby objects clearly but distant objects appear blurred.

  2. 2

    Add for 2 marks

    In myopia, light from a distant object is focused in front of the retina instead of on it.

  3. 3

    Add for 3 marks

    This can happen because the eyeball is too long or the eye lens has too much converging power.

MCQ Quiz

Practice this concept with focused MCQs

Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.

10 MCQs5 MinutesInstant Results
Practice This Concept

Help improve this page

Found something confusing, incorrect, or missing?

Practice This Concept