Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 9

# Reflection of Sound

#### Topics

• ##### Force
• Force
• Translational and Rotational Motions
• Moment (Turning Effect) of a Force Or Torque
• Couple
• Equilibrium of Bodies and Its Types
• Principle of Moments
• Centre of Gravity
• Uniform Circular Motion (UCM)
• Centripetal Force
• Centrifugal Forces
• ##### Machines
• Machines
• Simple Machines
• Technical Terms Related to a Machine
• Principle of Machine
• Relationship between efficiency (ղ), mechanical advantage (M.A.) and velocity ratio (VR)
• Lever
• Kinds of Levers
• Examples of Each Class of Levers as Found in the Human Body
• Pulley
• Single Fixed Pulley
• Single Movable Pulley
• Combination of Pulleys
• Machines (Numerical)
• ##### Refraction of Light at Plane Surfaces
• Refraction of Light
• Law of Refraction of Light
• Speed of Light
• Relationship Between Refractive Index and Speed of Light (µ = C/V)
• Principle of Reversibility of the Path of Light
• Experimental Verification of Law of Refraction and Determination of Refractive Index of Glass
• Refraction of Light Through a Rectangular Glass Slab
• Multiple Images in a Thick Plane Glass Plate Or Thick Mirror
• Prism
• Refraction of Light Through a Prism
• Real and Apparent Depth
• Apparent Bending of a Stick Under Water
• Some Consequences of Refraction of Light
• Transmission of Light from a Denser Medium (Glass Or Water) to a Rarer Medium (Air) at Different Angles of Incidence
• Critical Angle
• Relationship Between the Critical Angle and the Refractive Index (µ = 1/ Sin C)
• Total Internal Reflection
• Total Internal Reflection in a Prism
• Use of a Total Internal Reflecting Prism in Place of a Plane Mirror
• Consequences of Total Internal Refraction
• ##### Spectrum
• Deviation Produced by a Triangular Prism
• Colour in White Light with Their Wavelength and Frequency Range
• Dispersion of Light Through Prism and Formation of Spectrum
• Electromagnetic Spectrum
• Different Radiation of Electromagnetic Spectrum
• Gamma Rays
• X rays
• Visible Light
• Micro Waves
• Scattering of Light and Its Types
• Applications of Scattering of Light
• ##### Sound
• Sound
• Difference Between the Sound and Light Waves
• Reflection of Sound
• Echoes
• Determination of Speed of Sound by the Method of Echo
• Use of Echoes
• Natural Vibrations
• Damped Vibrations
• Forced Vibrations
• Resonance
• Demonstration of Resonance
• Some Examples of Resonance
• Properties of Sounds
• Loudness and Intensity
• Pitch (or shrillness) and frequency
• Audibility and Range
• Quality (Or Timbre) and Wave Form
• Noise Pollution
• Noise and Music
• Sound (Numerical)
• ##### Household Circuits
• Transmission of Power from the Power Generating Station to the Consumer
• Power Distribution to a House
• House Wiring (Ring System)
• Electric Fuse
• Miniature Circuit Breaker (MCB)
• Electric Switch
• Circuits with Dual Control Switches (Staircase Wire)
• Earthing (Grounding)
• Three-pin Plug and Socket
• Colour Coding of Live, Neutral, and Earth Wires
• High Tension Wires
• Precautions to Be Taken While Using Electricity
• ##### Calorimetry
• Heat and Its Unit
• Temperatures
• Factors Affecting the Quantity of Heat Absorbed to Increase the Temperature of a Body
• Difference Between Heat and Temperature
• Thermal Capacity (Heat Capacity)
• Specific Heat Capacity
• Relationship Between the Heat Capacity and Specfic Heat Capacity
• Specific Heat Capacity of Some Common Substances
• Calorimetry and Calorimeter
• Principle of Method of Mixtures (or Principle of Calorimetry)
• Natural Phenomena and Consequences of High Specific Heat Capacity of Water
• Some Examples of High and Low Heat Capacity
• Change of State of Matter
• Melting and Freezing
• Heating Curve of Ice During Melting
• Change in Volume on Melting
• Effect of Pressure on the Melting Point
• Effect of Impurities on the Melting Point
• Concept of Boiling (Vaporization)
• Heating Curve for Water
• Change in Volume on Boiling
• Effect of Pressure on the Boiling Point
• Effect of Impurities on the Boiling Point
• Latent Heat and Specific Latent Heat
• Specific Latent Heat of Fusion of Ice
• Explanation of Latent Heat of Melting on the Basis of Kinetic Model
• Natural Consequences of High Specific Latent Heat of Fusion of Ice
• Structure of the Atom and Nucleus
• Atomic Model
• Isotopes
• Isobars
• Isotones or Isoneutronic
• Properties of Alpha Particles
• Properties of Beta Particles
• Changes Within the Nucleus in Alpha, Beta and Gamma Emission
• Alpha Decay (Alpha Emission)
• Beta Decay (Beta Emission)
• Gamma Decay (Gamma Emission)
• Safety Precautions While Using Nuclear Energy
• Nuclear Energy
• Nuclear Fission
• Distinction Between the Radioactive Decay and Nuclear Fission
• Nuclear Fusion
• Distinction Between the Nuclear Fission and Nuclear Fusion
• Reflection of Sound
• Reflection of sound in a different medium
1. Reflection at the boundary of a denser medium
2. Reflection at the boundary of a rarer medium
3. Reflection of sound in the plane and curved surfaces

## Notes

Reflection of sound:

Sound can bounce off a solid or a liquid. Some materials like metals and walls are called Good Reflectors of Sound as they do not absorb the sound while others like clothes and sponge are called Bad Reflectors of Sound as they absorb the sound easily.

Laws of reflection

There are two basic laws of reflection of sound:

(i) Angle of incidence is equal the angle of reflection.

(ii) The incident wave, the reflected wave and the normal all lie in the same plane.

Applications of Reflection of Sound

## Notes

Uses of multiple reflection of sound:

• Horns, trumpets, loudhailers or megaphones are designed in such a way that sound can travel in a particular direction only without spreading out everywhere. This makes it easier for the audience to listen to the speaker. All these instruments work on the phenomena of multiple reflections of sound.
• Stethoscope is a medical instrument used for listening to sounds produced within the body, mainly in the heart or lungs. In stethoscopes the sound of the patient’s heartbeat reaches the doctor’s ears by multiple reflection of sound
• Generally the ceilings of concert halls, conference halls and cinema halls are curved so that sound after reflection reaches all corners of the hall, Sometimes a curved soundboard may be placed behind the stage so that the sound, after reflecting from the sound board, spreads evenly across the width of the hall.
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