Monday 30 January 2017

Class - 9 / SOUND / VIDEO SUBSCSRIBING LINKS

SOUND introduction :



BELL JAR Experiment :




Characteristics of sound waves :





Experiment to calculate propagation velocity of sound wave through SLINKY :





Experiment to verify LAWS OF REFLECTION :





Application of ULTRASONIC SOUND :





SONAR :




HUMAR EAR structure :






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Tuesday 24 January 2017

PHYSICS LAB EXPERIMENT

EXPERIMENT # 4
LAWS OF REFLECTION OF SOUND

Our Objective
To verify the laws of reflections of sound.




The Theory

What is reflection?
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.
Do you know how sound propagates?
Sound propagates through air as a longitudinal wave. The speed of sound is determined by the properties of the air, and not by the frequency or amplitude of the sound.  If a sound is not absorbed or transmitted when it strikes a surface, it is reflected. The law for reflection is the same as that of light, ie., the angle of incidence of a sound wave equals the angle of reflection, just as if it were produced by a 'mirror image' of the stimulus on the opposite side of the surface.
How do we describe the reflection of sound?
When sound travels in a given medium, it strikes the surface of another medium and bounces back in some other direction, this phenomenon is called the reflection of sound. The waves are called the incident and reflected sound waves.
What are incident and reflected sound waves?
The sound waves that travel towards the reflecting surface are called the incident sound waves. The sound waves bouncing back from the reflecting surface are called reflected sound waves. For all practical purposes, the point of incidence and the point of reflection are the same point on the reflecting surface.
A perpendicular drawn on the point of incidence is called the normal. The angle which the incident sound waves makes with the normal is called the angle of incidence, "i". The angle which the reflected sound waves makes with the normal is called the angle of reflection, "r".
Let’s look at the two laws of reflection
The following two laws of reflection of light are applicable to sound waves as well:
  • The incident wave, the normal to the reflecting surface and the reflected wave at the point of incidence lie in the same plane.
  • The angle of incidence ∠i is equal to the angle of reflection ∠r.
Materials Required:
Protractor table with two hollow tubes and a reflecting surface, alarm clock

Procedure:
1.     Take a sound reflection apparatus that consists of two hollow cylindrical tubes, a sound reflecting surface and a protractor.
2.     Move tube 1 towards left at an angle of 200 on the protractor.
3.     Now take a alarm clock and position it at the mouth of tube 1.
4.     You can hear sound waves passing through tube 1.now move tube 2 to catch the sound wave from tube 1. Once the maximum intensity is obtained through tube 2,fix the tube at that angle.
5.     Note the angle of incident and angle of reflection.
6.     Repeat the same above steps by moving tube 1 and then tube 2 at various angles.

Observations: 


Result: 
The angle of incidence is equal to angle of reflection.

Learning Outcomes
Student will understand the First and Second Laws of Reflection.

First Law of Reflection: The incident wave, the reflected wave, and the normal at the point of incidence lie on the same plane.

Law of Reflection: The angle of incidence is equal to the angle of reflection.

NOTE: he video for this can be subscribe through the given link:
https://www.youtube.com/watch?v=5bT0BQx9UI8#action=share






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PHYSICS LAB EXPERIMENT

EXPERIMENT # 5
Velocity of a Pulse Propagated Through a Slinky

Our Objective
To determine the velocity of a pulse propagated through a slinky or a stretched string.
The Theory
What is meant by a slinky?
A slinky is a long helical spring, usually made of steel. It is flexible and has appreciable elasticity. It produces transverse waves when one end is fixed and the other end is stretched and given a jerk at right angle to its length. It produces longitudinal waves when compressions are given at regular intervals of time at the free end of the slinky. A disturbance which propagates through a medium is called wave.
What are longitudinal waves?
In case of longitudinal waves, the particles of the medium vibrate to and fro periodically along the direction of propagation of the wave. It consists of alternate compressions and rarefactions. For example, waves along a compressed spring are longitudinal waves.


Wavelength (λ) of longitudinal waves can be defined as:
The distance covered by one complete rarefaction and one complete compression. [Or] The distance between two consecutive compressions or rarefactions.
Frequency:  The number of vibrations made by a particle in the slinky per unit time (one second) is called its frequency. It is denoted by the symbol ‘f’.
Materials Required:

Procedure:
For Transverse Waves
1.     Take a slinky and place it lengthwise on the smooth surface of the table.
2.     Tie one end of the slinky with the fixed hook.
3.     Hold the free end of the slinky and stretch it (1 to 3 m depending upon the nature of slinky).
4.     Move your hand periodically and uniformly at right angles to the length of the slinky.
5.     Observe the propagation of the wave through the slinky and observe  the formation of crests and troughs.
For Longitudinal Waves
6.     Compress the free end of the slinky periodically and observe the slinky.
Did you see an alternate compressions and rarefactions passing through the slinky?
7.     Measure the wavelength by measuring the distance between two consecutive troughs (T and T) or two crests (C and C) in case of transverse wave. In case of longitudinal wave, λ is equal to distance between two consecutive compressions (C and C) or rarefactions (R and R).
8.     Note the time as pulse (wave) passes through slinky for a particular distance from which we can find out the velocity of the wave.

 Calculations:
       VELOCITY, V = DISTANCE TRAVELLED / TIME TAKEN

Observations: 
Length of slinky (cm)
Distance travelled by the pulse (cm )
Distance travelled by the pulse (m)
Time (s)            
Velocity = Distance/time (m/s)
 500
500 
5 
4.6 
1.06 
 300
300 
3 
2.8 
1.07 

Result: 
The velocity of a pulse (wave) propagated through a stretched slinky = 1.06 m/s
Precautions:
1.     The slinky should have appropriate length, elasticity and flexibility.
2.     One end of the slinky should be fixed properly.
3.     The top of the table should be smooth.


 NOTE : THE VIDEO FOR THIS CAN BE SUBSCRIBE THROUGH THE LINK GIVEN:

https://www.youtube.com/watch?v=FUBGrH-PbsU#action=share






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Saturday 21 January 2017

class 5 - E.V.S - 17(TRAVEL & FUEL)

UNIT- 17, TRAVEL AND FUEL
QUICK LEARNING BITS
    1.      Vehicles generally run on two kinds of fuels-
a.      Petrol and diesel                    
b.      CNG and LPG
    2.      Fuel is the source of energy-
a.      True
b.      False
    3.      People prefer petrol and diesel over CNG because-
a.      CNG causes less pollution
b.      CNG availability is less
    4.      Vehicles run on-
a.      Fuels
b.      Oxygen
    5.      Small vehicles like motorbike, scooters generally run on-
a.      Petrol
b.      Diesel
    6.      Heavy vehicles like trucks, buses generally move on-
a.      Petrol
b.      Diesel
    7.      Fuel which makes everyday driving cheaper-
a.      Diesel
b.      Petrol
    8.      The energy output per unit volume of petrol is better than diesel-
a.      True
b.      False
    9.      Airplanes use special type of fuel called-
a.      Fossil fuel
b.      Aviation fuel
    10.  Fuels used in dry cleaning, making crayons, deodorants etc-
a.      Petroleum
b.      Biogas
    11.  Coal, petroleum and natural gas are-
a.      Renewable fuels
b.      Non-renewable fuels
    12.  Fossil fuels are also known as-
a.      Renewable fuels
b.      Non-renewable fuels
    13.  Which of the energy source is non-renewable-
a.      Fossil fuels
b.      Biomas
    14.  Renewable resources are-
a.      Eco-friendly
b.      Harmful to environment
    15.  Which of the following non-renewable energy source is NOT a fossil fuel-
a.      Oil
b.      Nuclear
    16.  Beside oil, what else is found deep inside the earth?
a.      Natural gas
b.      Biogas
    17.  Which fossil fuel is formed by decaying of plant matter?
a.      Coal
b.      Petroleum
    18.  Products obtained from petroleum-
a.      Diesel, petrol, kerosene
b.      Gobar gas, bio fuels, coal
    19.  A renewable resource can take many-many generations to replenish itself?
a.      True
b.      false
    20.  Which of the energy source is renewable-
a.      Peat
b.      Hydropower
    21.  CNG is preferred over petrol and diesel because-
a.      Eco-friendly
b.      Cheap
    22.  Solar energy is renewable resource-
a.      True
b.      False
    23.  CNG stands for-
a.      Coal nature gas
b.      Compressed natural gas
    24.  Non-renewable means resources that can be regenerate quickly-
a.      True
b.      False
    25.  Wind energy is non-renewable resource-
a.      True
b.      False
    26.  LPG stands for-
a.      Liquefied petroleum gas
b.      Liquefied pollution less gas
    27.  Renewable means resources that can be regenerate quickly-
a.      True
b.      False 
    28.  Renewable resources are-
a.      Naturally available which can replenish quickly
b.      Naturally available which can take many-many genarations to replenish
    29.  Fossil fuels formed hundreds of millions of years ago from the remains of dead?
a.      Animals and plants
b.      Plants and bones
    30.  Non-Renewable resources are-
a.      Naturally available which can replenish quickly
b.      Naturally available which can take many-many generations to replenish
    31.  Coal is the fossil fuel to burn, releasing many air pollutants.
a.      True
b.      False
    32.  What is smog made of?
a.      Fog and coal
b.      Fog and smoke
    33.  Factories produce-
a.      Harmful gases
b.      Oxygen
    34.  Burning of fossil fuels emits gases like-
a.      Carbon monoxide and nitrogen oxides
b.      Carbon dioxide and natural gas
    35.  The amount of air pollution caused by vehicles can be controlled by-
a.      Reducing number of vehicles on road
b.      Regenerating more number of vehicles on road
    36.  Natural gas is found along with-
a.      Coal
b.      Petroleum
    37.  Fuels are expensive and should be used when-
a.      One feel like using
b.      Necessary
    38.  Non-renewable fuels, when used, release harmful substances causes-
a.      Population
b.      Pollution
    39.  Black gold is-
a.      Crude oil
b.      Coal
    40.  Air pollution causes-
a.      Health problems
b.      Financial problem


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