Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Waves and optics → Light Waves and Optics ↓


Lenses and Image Formation


Lenses are transparent objects made of glass or plastic that refract light rays, meaning they bend light rays as they pass through. Lenses are used primarily to focus or disperse light in instruments such as eyeglasses, cameras, microscopes, and telescopes. In this talk, we will explore lenses and the formation of images, discussing key concepts, real-world applications, and many examples.

Types of lenses

There are two main types of lenses:

  1. Convex lens: Also known as a converging lens, this lens is thicker at the center than at the edges. It converges light rays passing through it, focusing them at a single point.
  2. Concave lens: Also known as a diverging lens, this type is thinner at the center than at the edges. It diverges light rays, spreading them farther apart.

Convex lens

A convex lens is attractive because it can form an image by focusing light rays. It is typically oval-shaped, with the middle bulging outward. The principal axis is an imaginary line that passes through the optical center of the lens. The point where all the light rays meet after passing through the lens is known as the focal point. Let's look at this with a simple example.

Focal point Main axis

In the above view, you can see a convex lens refracting light rays. Notice how the incoming parallel light rays bend toward each other as they exit the lens. The point at which they converge is the focal point.

Image formation by a convex lens

Convex lenses can form both real and virtual images, depending on the position of the object relative to the lens. Below are a few scenarios that demonstrate this:

1. Object beyond 2F

When an object is placed further than twice the focal length (2F) of a convex lens, the image formed is:

  • Real and inverse
  • Decrease in size
  • Located between F and 2F on the opposite side of the lens
2F F

2. Object at 2F

When the object is exactly at 2F, the image:

  • is real and inverted
  • is the same size as the object
  • is located at 2F on the other side of the lens

3. Object between F and 2F

If the object lies between the focal point (F) and twice the focal length (2F):

  • The image is real and inverted
  • magnified
  • Beyond 2F

4. On object F

When the object is at the focal point (F), the refracted rays become parallel, and no image is formed. This is because parallel lines do not meet.

5. Object between lens and F

When the object is between the lens and the focal point, the image formed is:

  • Virtual
  • Honest
  • magnified
  • appears on the same side as the object

Lens formulas

The lens formula is used to calculate the position of the image formed by a lens. It is given as:

1/v - 1/u = 1/f

Where:

  • v is the image distance
  • u is the distance to the object
  • f is the focal length of the lens

Magnification

Magnification is the process in which the size of the image is increased or decreased in comparison to the object. Magnification (M) is given by:

M = h_i/h_o = v/u

Where:

  • h_i is the height of the image
  • h_o is the height of the object

Concave lens

A concave lens, on the other hand, diverges or spreads the light rays passing through it. Concave lenses have their own unique properties as well. While concave lenses usually form virtual, smaller and images facing the same direction as the object, they have important applications in optics.

Main axis

In the case of a concave lens, all images are generally:

  • virtual and erect
  • Decrease in size
  • on the same side as the object

Real-world applications

1. Glasses

Lenses in eyeglasses are used to correct vision. People who are nearsighted use concave lenses to help them see distant objects more clearly, while people who are farsighted use convex lenses to help them see close-up objects.

2. Camera

Cameras use convex lenses to focus light onto the film or digital sensor, producing sharp images. The ability of a camera lens to focus light defines the clarity and quality of photos.

3. Magnifying glass

Magnifying glasses use convex lenses. When an object is placed close to the lens (within the focal length), a virtual, magnified image is formed, helping people see small details.

Conclusion

Understanding lenses and image formation is fundamental in optics and plays a vital role in a variety of technical and scientific fields. Whether correcting vision, capturing beautiful photographs or aiding scientific research, the principles of lenses continue to inspire innovations and discoveries.


Grade 10 → 4.3.7


U
username
0%
completed in Grade 10

← Prev (4.3.6)
Snell's Law
Next (4.3.8) →
Total internal reflection and critical angle

Comments 



Lenses and Image Formation

https://www.physicsflow.com/g10/4.3.7?pfal=en