You are in Class 10 and looking for Science Chapter 10 Light notes. Then this complete guide is here to help you. These notes cover all the important NCERT and CBSE concepts in basic language. Useful for revision, school exams, and board exams.
The light is
Light is a type of energy that allows us to see things and objects. We can only see an object when light enters our eyes.
And explains the main point of this chapter:
Light Reflection a
Spherical Mirrors
Refraction of Light
Lenses
Human Eye
Defects of Vision
1. Reflection of Light
Reflection of light is when light falls on a shiny surface and bounces back.
Important Terms to Think About
| Term | Meaning |
| Incident Ray | A ray of light falling onto a surface |
| In Reflected Ray | a Ray of light that is reflected |
| Normal | In a perpendicular of a line is at the point of a incident. |
| Angle of Incidence | an angle between the incident ray and a normal |
| Angle of Reflection | an angle between reflected ray and a normal |
Laws of Reflection
1. The angle of incidence is equal to an angle of reflection of light.
2. A normal lies in a same plane only with an incident ray, or a reflected ray.
2. Reflection Types
| Type: | Surface | Example |
| In Regular Reflection. | A smooth surface | On the mirror |
| In irregular reflection | In a rough surface | On the Wall |
3. Spherical mirrors
Spherical mirrors are mirrors with curved and reflective surfaces.
Types of a Spherical Mirrors
| Mirror Type | Shape | Uses |
| In the concave mirror | It’s curved inwards | We use torches, shaving mirrors, and headlights. |
| Inside a Convex Mirror | it’s curved outwards | through a rear-view mirror |
Key Terms
- Pole (P): Centre of mirror surface
- Curvature center (C)
- Curvature Radius (R)
- Principal axes
- Focus (F)
- Focal Length (f): Distance between P and F
4. Image Formation by Concave Mirror
| Object Position | Image Position | Nature of Image |
| Infinite | At Focus on | Real, diminutive, invert |
| Beyond C | Between C & F | Real and Inverted |
| At C | At C | In a Same size |
| Between C and F | Beyond C | Enlarged |
| At F | Infinity | Highly enlarged |
| Between F and P | Behind mirror | Virtual, elevated, and magnified. |
5. Image formation using convex mirrors.
The image always forms behind a mirror.
It created a virtual and erect
It is formed of a diminished
6. Mirror Formula.
Where:
f represents the focal length.
v represents image distance.
u represents the object’s distance.
7. Magnification in a Mirrors
Where:
hi = height of image
ho= height object
8. Refraction of Light
The Refraction of light is the bending of light as it moves from one medium to another.
For Example:
- Pencil looks bent in water
- coin is raised in water is appears
Rules of Refraction
1. Light bends towards normal when it enters a denser medium.
2. When light passes from a rarer medium to a denser one, it bends away from the normal.
9. Refractive Index
A refractive index is a measurement of how much light bends when it passes from one medium to another.
Simple Definition:
In the ratio of the speed of light in a vacuum to the speed of light in a given medium.
n = c/v
Where:
n = is refractive index
c = speed of light in vacuum
v = speed of a light in medium
Simple Meaning:
Higher refractive index = has light slow down more and it bends more.
A lower refractive index means light bends less.
For Examples:
Medium Refractive Index
Air = 1.0003
Water == 1.33
Glass == 1.5
Diamond ==2.42
10. Lenses
A transparent material bounded by a two surfaces is called a lens.
| Lens Type | Shape | Nature |
| In Convex Lens | Thick in a middle | Is Converging lens |
| In Concave Lens | Thin in a middle | It is a diverging lens |
11. Image Formation by Convex Lens
| Object Position | Image Position | Nature |
| At Infinity | At Focus | Real and diminished |
| Beyond 2F | Between F and 2 F | Real and inverted |
| At the 2F | At 2 F | in a Same size |
| Between F and 2F | Beyond 2 F | Enlarged |
| Between F and O | Same side of lens | Virtual and erect |
12. Lens Formula
The Lens Formula gives the relation between object distance image distance and focal length.
1/f = 1/v – 1/u
Where it:
- f = focal length of a lens
- v = image of distance
- u = object of a distance
Sign Convention:
- Object distance (u) is usually negative
- Real image is distance (v) is positive
- A convex lens has a focal length (f) is a positive
- A concave lens is focal length (f) is negative
Magnification Formula:
m = v/u = hi/ho
- Magnification (m)
- (hi) the image’s height
- (ho ) object height
13. Magnification by Lens
13. Magnification by Lens
The magnification produced by a lens is the ratio of height of the image to the height of the object.
Where it
- m = magnification
- hi = height of a image
- ho = height of a object
- v = image of distance
- u = object of distance
Meaning of Magnification:
- m > 1 = enlarged image
- m = 1 = same size of image
- m < 1 = diminished of a image
Nature of Image:
- Positive magnification = Is virtual and the erect image
- Negative magnification = Is real and the inverted image
14. Power of Lens
The power of a lens is the measure of its ability to converge or diverge light.
Unit = Diopter (D)
A convex lens has positive power
A concave lens has negative power
15. Human Eye
Main Parts of Human Eye
- Cornea
- Iris
- Pupil
- Eye Lens
- Retina
- Optic Nerve
16. Defects of Vision and Their Correction( important )
| Defect | Problem | Corrected By |
| In Myopia | We can see far objects blurred | Concave lens |
| In Hypermetropia | We can see near objects blurred | Convex lens |
| In Presbyopia | Old age vision problem | Bifocal lens |
17. Important Formulas Revision
| No. | Formula Name | Formula | Use |
| 1 | Mirror Formula | 1/f = 1/v + 1/u | To find a focal length, image distance, and object distance |
| 2 | Magnification by Mirror | m = h(i)/h(o) = -v/u | To find the size and nature of the image |
| 3 | Lens Formula | 1/f = 1/v – 1/u | To find focal length, image distance, object distance |
| 4 | Magnification by Lens | m = h(i)/h(o) = v/u | To find an image size formed by a lens |
| 5 | Power of Lens | P = 1/f | To find a power of lens |
| 6 | Power Unit | 1 Dioptre = 1 m⁻¹ | the SI unit of power |
| 7 | Combination of Lenses | P = P1 + P2 + P3 | the total power of a lenses |
FAQs
Q1. What is a reflection of light?
Ans: Reflection of light is the bouncing back to a surface.
Q2. What is a refraction of light?
Ans: When refraction of light bending occurs, it passes from one medium to another medium .
Q3. Which lens is used in myopia?
Ans: We use a concave lens.
Q4. What is the lens of unit of power?
Ans: Dioptre.
Conclusion
Light chapter is a very good chapter and an interesting chapter of Class 10 science. If you understand reflection, refraction, mirrors, lenses, and the human eye properly, you can score very good marks in exams.