Class 10 Light, Reflection & Refraction Mind Map for Last Minute Board Revisions

Class 10 Science board exam 2026 is scheduled on February 25, 2026 students are now in the most crucial stage of revision. The chapter Light: Reflection & Refraction is an important part of the syllabus and covers key concepts such as laws of reflection, mirror and lens formulas, refraction through different media, and the formation of images. This chapter is concept-based and often appears in exams through definitions, numerical problems, diagram-based questions, and real-life applications.

To make last-minute revision faster and more effective, a mind map–based explanation can help students connect all the key concepts in a clear and organized way. This approach ensures that important points are easy to grasp, helping students revise quickly and confidently.

For a better understanding, students can also watch the Light: Reflection & Refraction Mind Map on the Physics Wallah Foundation YouTube Channel. The mind map explains all important terminology in the simplest way possible, making it a perfect tool to boost Class 10 Science board exam preparation.

Class 10 Light and Its Properties Mind Map Series

The chapter Light and Its Properties is an important part of the Class 10 Science syllabus and carries significant weight in board exams. Many students find it challenging because it includes multiple interconnected concepts such as reflection, refraction, laws of light, mirror and lens formulas, and image formation. To make learning easier and revision more effective, a simple and organized mind map approach can be very helpful.

Also Watch: Light and Its Properties Mind Map

This mind map video presents the entire chapter in a clear, connected format, making concepts easy to understand and helping students revise quickly and confidently for the Class 10 Science board exam.

Light and its Properties Overview

Light, a fundamental form of energy, allows us to perceive the world and forms an important part of the Science 10th class board exam 2026. This exploration covers its essential properties and two key phenomena: reflection and refraction. 

1. Light and its Properties

Light is a form of energy that produces the sensation of sight, enabling us to see objects.

• Properties of Light:

1. Speed: Light propagates at a speed of 3 x 10⁸ m/s in a vacuum or free space. Its speed is slightly less in air, but this value is used as a close approximation.

2. Rectilinear Propagation: Light tends to travel in a straight line. This property is known as rectilinear propagation. (*Rectilinear: Straight line; Propagation: To move forward.)*

2. Reflection of Light

Reflection is the phenomenon of bouncing back of light after striking a polished surface, such as a mirror. A polished surface reflects most of the light that falls on it.

• Terminology:

• Incident Ray: The ray of light that strikes the surface.

• Reflected Ray: The ray of light that bounces back from the surface.

• Normal: An imaginary line drawn perpendicular (at 90°) to the surface at the point of incidence. It is used as a reference to measure angles.

• Angle of Incidence (i): The angle between the incident ray and the normal.

• Angle of Reflection (r): The angle between the reflected ray and the normal.

• CAUTION: The angles of incidence and reflection are NEVER measured with respect to the surface. They are always measured with respect to the normal.

3. Laws of Reflection

There are two fundamental laws of reflection:

1. The angle of incidence is always equal to the angle of reflection (∠i = ∠r).

2. The incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane. These three are co-planar.

4. Types of Images: Real vs. Virtual

5. Types of Mirrors

Mirrors are broadly classified into Plane Mirrors and Spherical Mirrors (Concave and Convex).

6. Image Formation by a Plane Mirror

In a plane mirror, an image is formed when at least two rays originating from the object are reflected and appear to meet behind the mirror.

• Properties of the Image Formed by a Plane Mirror:

1. Virtual and Erect: The image is formed behind the mirror and is upright.

2. Same Size: The size of the image is exactly the same as the size of the object.

3. Laterally Inverted: The image is flipped horizontally (e.g., the word "AMBULANCE" is written in a laterally inverted manner on the vehicle).

4. Equal Distance: The image is formed as far behind the mirror as the object is in front of it (Object distance = Image distance).

7. Spherical Mirrors

A. Concave Mirror

A spherical mirror whose reflecting surface is curved inwards. It is polished on the outer, bulging surface.

• Key Terms: Pole (P) (center of reflecting surface), Center of Curvature (C) (center of the sphere of which mirror is a part), Focus (F) (point where parallel rays converge after reflection, midpoint between P and C).

B. Convex Mirror

A spherical mirror whose reflecting surface is curved outwards. It is polished on the inner, hollow surface. The object is always placed on the left, and light is incident from the left side.

8. Rules for Ray Tracing in Spherical Mirrors

To construct a ray diagram, any two of the following four rules can be used.

9. Ray Diagrams: Image Formation by a Concave Mirror

• Special Case: The 6th case is important as it is the only one where a concave mirror forms a virtual and erect image.

• Uses: Headlights, torches, dentist's mirrors, makeup mirrors, shaving mirrors. 

10. Ray Diagrams: Image Formation by a Convex Mirror

• Key Characteristic: A convex mirror always forms a virtual, erect, and diminished image, regardless of object position. (*Memory Tip: Remember VED for Convex mirrors and Concave lenses: *V**irtual, **E**rect, **D**iminished).

• Uses: Rear-view mirrors in vehicles, road-view mirrors at sharp turns. They provide a wide field of view.

11. The Mirror Formula and Sign Convention

New Cartesian Sign Convention

1. The Pole (P) of the mirror is treated as the origin (0,0).

2. Distances measured to the right of the pole are positive (+).

3. Distances measured to the left of the pole are negative (-).

4. Heights measured upwards are positive (+).

5. Heights measured downwards are negative (-).

6. All distances are measured from the pole.

The Mirror Formula

The relationship between object distance (u), image distance (v), and focal length (f) is given by:

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

• Comparison: The mirror formula is 1/f = 1/v + 1/u, while the lens formula is 1/f = 1/v - 1/u.

12. Magnification (m)

Magnification is the ratio of the height of the image to the height of the object.

• Formula 1 (Height): $$ m = \frac{\text{Height of Image (h')}}{\text{Height of Object (h)}} $$

• Formula 2 (Distance): $$ m = -\frac{v}{u} $$

Interpreting Magnification

• Based on Value (Size):

• If |m| < 1, the image is diminished.

• If |m| = 1, the image is the same size.

• If |m| > 1, the image is enlarged.

• Based on Sign (Nature):

• If m is positive (+), the image is virtual and erect.

• If m is negative (-), the image is real and inverted.

13. Refraction of Light

Refraction is the phenomenon of the bending of light as it passes from one transparent medium to another.

• Cause: Refraction occurs because the speed of light changes when it enters a different medium due to differences in optical densities.

• Conditions:

1. Light must travel from one transparent medium to another.

2. Bending only occurs if the two media have different optical densities.

• Optical Density vs. Mass Density: Optical density determines how fast light travels through a medium, related to refractive index. This is NOT the same as mass density.

14. Laws of Refraction

1. The incident ray, the refracted ray, and the normal to the interface of the two media at the point of incidence, all lie in the same plane.

2. Snell's Law: The ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is a constant for a given pair of media and for light of a particular wavelength. $$ \frac{\sin i}{\sin r} = \text{constant} $$

• Conditions for the constant: The pair of media and the wavelength (color) of light must be fixed.

15. Refractive Index (n)

Refractive index is a measure of the optical density of a medium.

• Emphasis: The formula is for the medium into which the light enters, with its speed in the denominator. For n₂₁, v₂ is in the denominator.

16. Spherical Lenses

• Convex Lens (Converging Lens): Thicker at the center, thinner at edges. Converges parallel rays.

• Concave Lens (Diverging Lens): Thinner at the center, thicker at edges. Diverges parallel rays.

• Key Terms: Optical Centre (O), Principal Foci (F₁, F₂), 2F₁ and 2F₂ (analogous to C in mirrors).

17. Rules for Ray Tracing in Lenses

18. Ray Diagrams: Image Formation by a Convex Lens

• Special Case: The 6th case is important as it forms a virtual and erect image, where the convex lens acts as a magnifier.

19. Ray Diagrams: Image Formation by a Concave Lens

A concave lens always produces a virtual, erect, and diminished image.

20. Lens Formula and Magnification

Sign Convention

All distances are measured from the optical center (O). Distances to the left are negative, to the right are positive. Heights above the principal axis are positive, below are negative.

Lens Formula

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

Magnification (m)

• For a Lens: $$ m = +\frac{v}{u} $$

• For a Mirror: $$ m = -\frac{v}{u} $$

• Common Definition: $$ m = \frac{\text{Height of Image}}{\text{Height of Object}} $$

21. Power of a Lens (P)

The power of a lens measures its degree of convergence or divergence. It is the reciprocal of its focal length.

• Formula: P = 1/f

• CAUTION: This formula is only valid when the focal length (f) is expressed in meters. The unit for power is the diopter (D).

• (*Memory Tip: Use P = 1/f when f is in meters, or P = 100/f when f is in centimeters to get power in diopters).*

22. Chapter Formula Sheet Summary

• Radius of Curvature: R = 2f

• Mirror Formula: 1/f = 1/v + 1/u

• Lens Formula: 1/f = 1/v - 1/u

• Magnification (Mirror): m = -v/u

• Magnification (Lens): m = +v/u

• General Magnification: m = h'/h

• Absolute Refractive Index: n_medium = c / v_medium

• Relative Refractive Index: n₂₁ = v₁ / v₂ = λ₁ / λ₂

• Snell's Law: sin(i) / sin(r) = n₂₁

• Power of a Lens (f in meters): P = 1/f

• Power of a Lens (f in centimeters): P = 100/f

• Combination of Lenses: P_net = P₁ + P₂ + P₃ + ... (Convex lens: positive power, Concave lens: negative power).