How do rays behave when they reflect from a concave mirror?

Parallel rays to the principal axis converge at the focal point after reflection.

How do rays behave when they reflect from a convex mirror?

Parallel rays to the principal axis appear to diverge from the focal point behind the mirror.

What kind of image is formed by a convex mirror?

A convex mirror always forms a virtual, erect, and reduced image.

What is the virtual focus of a convex mirror?

The focal point of a convex mirror is virtual and lies behind the mirror.

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Mirrors

Master Mirror Optics in Minutes Understand how light behaves when it strikes plane and spherical surfaces. Master the laws of reflection, the sign convention rules, and the mathematical calculations behind the mirror formula and magnification without messy code formatting.

Class: 10 Science (CBSE)
Chapter: Light – Reflection and Refraction
Estimated Learning Time: 20–25 Minutes

1.0Learning Outcomes

After completing this lesson, you will be able to:

State the Laws of Reflection and identify the properties of an image formed by a plane mirror.
Differentiate between Concave (converging) and Convex (diverging) spherical mirrors.
Identify the key terms of spherical optics: Pole, Center of Curvature, Principal Focus, and Focal Length.
Apply New Cartesian Sign Convention rules accurately to numerical problems.
Utilize the Mirror Formula and Magnification equations to calculate image attributes.

Introduction to Mirrors

A mirror is a smooth surface often made of glass with a reflective coating, usually either silver or aluminium, where the light is reflected to form an image. Mirrors are used frequently in many applications such as personal grooming, telescopes, cameras, and a part of scientific instruments.

2.0Types of Mirror

Mirrors are divided into three types based on their shapes:

Plane Mirrors
Concave Mirrors
Convex Mirrors

Concave and Convex are collectively called Spherical mirrors, which are curved mirrors on either side and affect their properties.

Plane Mirrors

Plane Mirrors have a flat reflective surface. It creates an image that is:

The image formed by any plane mirror is virtual; that is, it can not be projected on the screen.
The image created is always upright and in the same orientation as the object.
The image produced is of the same size as the object.
The image created is laterally inverted, meaning the left and right sides of the image are reversed.
The image produced is of equal distance of the object from the mirror.
The image formed is always behind the mirror.

Uses of Plane Mirrors

Plane Mirrors are used for personal grooming in the bathrooms and dressing rooms.
Plane mirrors can also be used for decorative purposes like in homes, offices, and vehicles.

Spherical Mirrors

Spherical mirrors are the type of mirrors whose reflecting surface forms part of a sphere. These can further be divided into two types:

Concave Mirrors (Converging mirrors)
Convex Mirrors (Diverging mirrors)

3.0Concepts Related to Spherical Mirrors

1. Center of Curvature(C): It is the centre of that sphere from where the spherical mirror is taken.

2. Principle Axis(P): It is the imaginary line through the centre of curvature and midpoint of the reflecting surface(a’b’ or ab) of the mirror.

3. Focus: Focus is the point in the midpoint between the centre of curvature and the Principle axis. The distance between points F and P is known as the Focal length.

Concave Mirror (Converging Mirrors)

A concave mirror has an inwardly curved reflecting surface. This allows converging light rays to the focal point. The concave mirror forms real or virtual images; they are either erect or inverted.

Position of object	Figure	Position of image	Nature of image
Infinity		At Focus	Real, inverted, and highly Diminished
Beyond C		Between C and F	Real, inverted, and Diminished
At C		At C	Real, inverted, and same size
Between C and F		Beyond C	Real, inverted, and bigger than the object
At F		At Infinity	Real, inverted, and extremely big
Between F and P		In front of the mirror	Virtual, erect, and magnified

Convex Mirror

A convex mirror has an outward-curved surface. Rays diverge from the incoming rays and seem to appear to emanate from one point behind the mirror.

Position of Object

Diagram

Position of Image

Nature of Image

At Infinity

At Focus

Virtual, erect, and highly diminished

Anywhere in front of the mirror

Between P and F

Virtual, erect, and diminished

4.0Mirror Formula for Spherical Mirrors

The mirror formula for Spherical mirrors gives the following relationship between the focal length (f), object distance (u), and the image distance (v):

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

According to the sign convention:

f is the focal length, which is positive for convex mirrors and negative for concave mirrors.
v is the image distance for real images and the negative image distance for virtual images.
u is the object distance (always negative as per sign conventions).

5.0Spherical Mirror Questions

Problem 1: A concave mirror has a focal length of 15 cm. An object is placed 30 cm in front of the mirror. Find the position, size, and nature of the image formed.

Solution: f = –15cm, u = –30cm

Using the mirror formula

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

$\frac{1}{- 15} = \frac{1}{v} + \frac{1}{- 30}$

$\frac{1}{v} = \frac{1}{15} - \frac{1}{30}$

$- \frac{1}{v} = \frac{2 - 1}{30} = \frac{1}{30}$

v=-30cm

Hence, the image is real and inverted, placed on the centre of curvature, and of the same size.

Problem: A convex mirror has a focal length of 20 cm. An object is placed 40 cm in front of the mirror. Find the position and nature of the image.

Solution: f = 20cm, u = –40cm

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

$\frac{1}{20} = \frac{1}{v} + \frac{1}{- 40}$

$- \frac{1}{v} = \frac{1}{- 20} - \frac{1}{40}$

$- \frac{1}{v} = \frac{- 2 - 1}{40}$

$- \frac{1}{v} = - \frac{3}{40}$

v=40/3 cm

Hence the image will be formed behind the mirror and is virtual and erect.

Problem: A spherical mirror has a focal length of 12 cm. An object is placed 36 cm in front of the mirror, and the size of the image is bigger than the object. Find the position and nature of the image.

Solution: Given that the image of the spherical mirror is bigger than the object hence the spherical is the concave mirror. So,

f = -12 cm, u = –36cm

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

$\frac{1}{- 12} = \frac{1}{v} + \frac{1}{- 36}$

$- \frac{1}{v} = \frac{1}{12} - \frac{1}{36}$

$- \frac{1}{v} = \frac{3 - 1}{36} = \frac{2}{36} = \frac{1}{18}$

v=-18cm

The position of the image is in front of the mirror, and it is real and inverted.

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7.0Supporting Study Materials

This study material, including CBSE Notes and NCERT Solutions for the Chapter "Light - Reflection and Refraction" on Mirrors topics, is designed according to the latest CBSE Class 10 Science syllabus and NCERT guidelines. It provides clear explanations of key concepts, definitions, examples, and important questions to help students understand reflection, spherical mirrors (concave and convex), ray diagrams, mirror formulas, and magnification, and prepare effectively for examinations.

8.030-Second Revision

Laws of Reflection = Angle i = Angle r; incident, normal, and reflected rays lie in 1 plane.
Plane Mirror Image = Virtual, erect, same size, same distance, laterally inverted.
Concave Mirror = Converges light; f is negative; forms real or virtual images.
Convex Mirror = Diverges light; f is positive; always forms virtual, erect, and smaller images.
Radius vs Focus = R = 2 * f.
Mirror Formula = 1/v + 1/u = 1/f.
Magnification = m = hi / ho = -v/u. (Negative m = Real, Positive m = Virtual).
9.0PREVIOUS YEAR QUESTIONS (PYQs)
Q1. A concave mirror produces a three times magnified real image of an object placed at 10 cm in front of it. Where is the image located? (CBSE Board)
Answer
Step 1: Identify given parameters with signs.
Object distance (u) = -10 cm (negative by convention)
Magnification (m) = -3 (negative because the image is explicitly stated as real)
Step 2: Use the magnification relationship to find image distance (v).
m = - (v / u)
-3 = - (v / -10)
-3 = v / 10
v = -30 cm
Conclusion: The image is located at a distance of 30 cm in front of the mirror (on the same side as the object, as shown by the negative sign).
Q2. Name the type of mirror used in the following situations and give reasons for your choices:
a) Headlights of a car
b) Rear-view mirror of a vehicle (CBSE Board)
Answer
a) Headlights of a car: A Concave mirror is used. When a powerful light source (bulb) is placed precisely at the principal focus of the concave reflector, the mirror reflects the rays into a strong, parallel beam of light that travels long distances to illuminate the road.
b) Rear-view mirror of a vehicle: A Convex mirror is used. It always creates a virtual, erect, and diminished image of objects behind the vehicle. Because the images are smaller, a convex mirror provides a significantly wider field of view than a plane mirror, allowing drivers to monitor a larger area of traffic safely.
10.0Recommended Next Topics
Refraction of Light and Snell's Law
Image Formation Rules for Convex and Concave Lenses
Lens Formula, Magnification, and Optical Power calculations
Dispersion and Scattering of Light through a Prism

Join ALLEN!

(Session 2026 - 27)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.

Mirrors

Master Mirror Optics in Minutes Understand how light behaves when it strikes plane and spherical surfaces. Master the laws of reflection, the sign convention rules, and the mathematical calculations behind the mirror formula and magnification without messy code formatting.

Class: 10 Science (CBSE)
Chapter: Light – Reflection and Refraction
Estimated Learning Time: 20–25 Minutes

1.0Learning Outcomes

After completing this lesson, you will be able to:

State the Laws of Reflection and identify the properties of an image formed by a plane mirror.
Differentiate between Concave (converging) and Convex (diverging) spherical mirrors.
Identify the key terms of spherical optics: Pole, Center of Curvature, Principal Focus, and Focal Length.
Apply New Cartesian Sign Convention rules accurately to numerical problems.
Utilize the Mirror Formula and Magnification equations to calculate image attributes.

Introduction to Mirrors

A mirror is a smooth surface often made of glass with a reflective coating, usually either silver or aluminium, where the light is reflected to form an image. Mirrors are used frequently in many applications such as personal grooming, telescopes, cameras, and a part of scientific instruments.