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 ↓


Reflection of light


Introduction

Reflection is the change in the direction of a wavefront at an interface between two different media so that the wavefront returns to the medium from which it originated. In physics, it applies to many types of waves, including light.

Light plays an important role in our perception of the world. Reflection is one of the fundamental properties of light that allows us to see objects. When light falls on a surface, it returns back to the original medium. This is what we call reflection of light.

Nature of light

Before delving deeper into reflection, it is important to understand the nature of light. Light is a form of energy that behaves as both a wave and a particle. In the context of reflection, we consider light as a wave. Light waves are transverse electromagnetic waves, which means they consist of oscillating electric and magnetic fields that are perpendicular to each other and the direction of propagation of the wave.

Laws of reflection

There are two main laws of reflection:

  1. The angle of incidence is equal to the angle of reflection.
  2. The incident ray, the reflected ray and the normal to the surface of the mirror all lie in the same plane.

Understand with examples:

Angle of Incidence = Angle of Reflection
   ,                                                     
   | (reflective surface)    
   ,                                            
   ,                                               
   ,                                               
   | incident /                                        
   | ray /                                   
   ,                                  
   |------------|------------> Normal (Vertical)                                                
   ,                                   
   , reflect                                   
   | ray                                  
   ,                                
   ,                               
   ,                               
   ,                                 
   ,

Types of reflection

Reflection can be broadly classified into two types: regular reflection and diffused reflection.

Regular reflection

Regular reflection occurs on very smooth surfaces such as mirrors or still water. In this type of reflection, parallel light rays falling on the surface will all reflect at the same angle, and therefore remain parallel.

   , parallel light ->
   The rays are coming in
   ,              
   ,
   | /| Regular Reflection                           
   | / | (light rays remain parallel)                                                        
   ,
   ,
   |--------------- (smooth surface)
   ,

Diffuse reflection

Diffuse reflection occurs on rough surfaces like paper or unpolished wood. In this type, parallel incoming rays reflect in different directions. This is why you can see objects from different angles.

   , parallel light ->
   The rays are coming in
   ,          
   ,
   , /\ Diffuse reflection          
   | /   (light rays scatter)
   ,                                   
   ,                          
   |----/----/---- (rough surface)   
   ,                      
   ,                       
   ,

Reflection from a plane mirror

A plane mirror is a plane reflecting surface. When light reflects from a plane mirror, the laws of reflection hold true. The image formed by a plane mirror has the following characteristics:

  • It is virtual (cannot be projected onto a screen).
  • It's simple.
  • It is laterally inverted.
  • The size of the image is equal to the size of the object.
  • The distance of the image from the mirror is equal to the distance of the object from the mirror.

Example of image formation in a plane mirror:

   | | O | MI |                               
   ,                           
   | |_________|_______| < (plane mirror)      
   ,                          
   | | Side view  
   | | inverse        
   ,                                   
   | | O image| M object                            
   ,

Mirror formula and magnification

For spherical mirrors, there is a formula connecting the object distance (denoted by u ), the image distance (denoted by v ) and the focal length (denoted by f ):

 1/f = 1/v + 1/u

The formula for magnification (m) is given by the ratio of the image height (h') to the object height (h):

 m = h'/h = -v/u

In case of a plane mirror, the magnification is always 1 because the height of the image and the object is the same.

Spherical mirror

Spherical mirrors are mirrors with a consistent curve, which are divided into concave and convex mirrors depending on the direction of the reflecting surface.

Concave mirror

A concave mirror is a spherical mirror with an inwardly curved reflecting surface. Concave mirrors converge light and can form real, inverted images or virtual, erect images, depending on the position of the object.

   ,                              
   | --- Light
   | - /---F convergence
   ,
   ,                   
   ,

Convex mirror

Convex mirrors have a reflecting surface curved outward. Since convex mirrors diverge light, they form only virtual images that are upright and smaller than the object.

   ,                  
   ,                    
   ,                                 
   ,                      
   ,                  
   ,     
   ,

Applications of reflection

Reflection of light is used in many real-world applications:

  • Mirrors: Used in homes, cars, telescopes, etc.
  • Periscope: Use two plane mirrors to see through obstacles.
  • Reflecting telescopes: Use a mirror to collect and focus light from distant objects.
  • In cameras: Mirrors reflect light to form an image on the film or sensor.

Conclusion

Reflection is a phenomenon that occurs when light waves hit the boundary between two different media and return back to the original medium. This principle governs how we perceive and interact with our environment at every moment. Understanding reflection equips us with the fundamental knowledge needed to explore more complex optics concepts and appreciate their technological applications in daily life.


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Reflection of light

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