C
CraftExam
high importancemedium difficulty5 min

Spherical Mirror

A spherical mirror is a mirror whose reflecting surface forms part of a sphere.

In one line: Inner surface curves in and can magnify; outer surface curves out and widens the view.

Practice This Concept

Understand it

If the inner surface reflects, it is a concave mirror; if the outer surface reflects, it is a convex mirror. These mirrors are used because they can converge or diverge light and form different images depending on the object position.

Example

A dentist mirror is usually concave, while a vehicle rear-view mirror is usually convex.

Formula and rule

For a spherical mirror, the principal focus lies on the principal axis; for a small aperture mirror, focal length is half the radius of curvature, f = R/2.

See it worked out

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

Worked example

  1. 1A dentist wants a magnified upright image of a tooth.
  2. 2A concave mirror is chosen, and the tooth is placed close to the mirror so the image appears enlarged and erect.

Method you can reuse

  1. 1Check which surface reflects.
  2. 2Decide concave or convex.
  3. 3Match the mirror to the required image or field of view.

Sketch it in your answer

Draw the pole, principal axis, centre of curvature, focus, and show whether the mirror is concave or convex by marking the reflecting surface.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is a convex mirror used as a rear-view mirror in vehicles?

Think first, then show answer
A convex mirror is used because it gives a wide field of view and forms an erect diminished image, so the driver can see more traffic behind.

Common wrong answer

Saying a convex mirror gives a magnified image in rear-view use. In fact it gives a diminished image but shows a wider area.

Don't mix this up

Students often mix up concave and convex by looking only at the shape, not the reflecting surface.

Exam tip

Always identify the reflecting surface first; inner surface means concave, outer surface means convex.

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

Questions ask you to identify mirror type from its use, label parts of the mirror, or predict image nature.
  1. 1

    Enough for 1 mark

    A spherical mirror is a mirror whose reflecting surface forms part of a sphere.

  2. 2

    Add for 2 marks

    Example: A dentist mirror is usually concave, while a vehicle rear-view mirror is usually convex.

  3. 3

    Add for 3 marks

    If the inner surface reflects, it is a concave mirror; if the outer surface reflects, it is a convex mirror.

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