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 → Optical Instruments ↓


Telescope


Introduction

A telescope is a fascinating optical instrument that allows us to view distant objects in the universe. Just like a magnifying glass helps us see small things up close, a telescope is designed to view distant objects, such as stars, planets, and galaxies. In this article, we will learn in detail about the functioning of a telescope, its types, and the fundamental principles of optics that make it possible.

How do binoculars work?

A telescope collects light from a distant object and forms a magnified image of it. This is achieved by the use of lenses or mirrors. When light enters the telescope, it passes through a lens or reflects off a mirror and reaches a focal point where an image of the object is formed.

Fundamentals of optics

To understand how telescopes work it is necessary to understand the basics of optics, especially how light behaves when it hits lenses and mirrors.

Lens

Lenses are pieces of transparent material, usually glass or plastic, that refract (bend) light. The extent to which they bend light depends on their shape.

  • Convex lenses: These lenses are thicker in the middle than at the edges. They converge light rays to a point called the focal point.
  • Concave lens: These lenses are thin in the middle. They spread out the light rays.
Light penetration Lens Focal point

Mirror

Mirrors reflect light. There are mainly two types of mirrors used in optics:

  • Concave mirrors: These mirrors are curved inwards like a cave. They converge the light rays to a focal point.
  • Convex mirror: These mirrors are protruding outwards. They reflect the light rays away.
Light penetration mirror Focal point

Types of telescopes

Refracting telescope

Refracting telescopes use convex lenses to gather and focus light. The main lens is called the objective lens, and the image is viewed through a second lens called the eyepiece.

Here's how it works:

  1. The objective lens captures light coming from a distant object and bends the light rays to focus them at a single point.
  2. The eyepiece lens magnifies this focused light, helping us see the bigger picture.
objective lens Eyepiece

Refracting telescopes deliver stunning images with high contrast, but their main drawback is chromatic aberration, where colors can be slightly out of focus due to the lens' inability to bring all wavelengths of light into the same focal plane.

Reflecting telescope

Reflecting telescopes use mirrors to gather and focus light. The primary mirror at the back of the telescope reflects the light to the focal point.

  1. Light enters the telescope and hits the curved primary mirror.
  2. This mirror reflects the light to the secondary mirror or directly to the eyepiece.
primary mirror Eyepiece

Reflecting telescopes do not have problems with chromatic aberration and are generally more economical to produce when it comes to large diameter telescopes. However, they can sometimes present problems with properly aligning the mirrors.

Understanding binocular magnification

A key aspect of a telescope is its magnification power, which indicates how large an object appears when viewed with the naked eye. Magnification is determined by the focal length of the telescope's lens.

The formula for magnification (M) is:

M = (focal length of objective lens) / (focal length of eyepiece)

For example, if the objective lens in a telescope has a focal length of 1000 mm and the eyepiece has a focal length of 25 mm, then the magnification will be:

M = 1000mm / 25mm = 40x

This means that an object viewed through a telescope appears 40 times larger than when viewed with the naked eye.

Resolution and aperture

The resolving power of a telescope is its ability to distinguish between two closely spaced objects. It depends largely on the telescope's aperture, which is the diameter of the objective lens or mirror. A larger aperture allows more light to enter, producing clearer and more detailed images.

Large aperture Small aperture

Telescopes with larger apertures can capture more light, and are therefore better for viewing faint objects such as galaxies and nebulae.

Conclusion

Telescopes are extraordinary instruments that allow us to see the universe with remarkable clarity. By understanding the basic principles of optics and the types of telescopes available, we can appreciate the technology that brings distant stars and planets closer to our eyes. Whether using lenses or mirrors, each telescope has its own advantages and limitations, but together, they have greatly increased our understanding of the universe.

From Galileo's first telescopic explorations to the powerful telescopes used today, this instrument continues to be at the forefront of astronomical discoveries, connecting us to the vast, beautiful universe beyond Earth.


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Telescope

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