Short answer Question of physics - wave and Optics-part-1

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1. Why is a diver underwater unable to hear the sound produced in air outside?

Answer:

 Yes, a diver under water unable to hear the sound produced in air outside. When a portion of sound is produced in air outside and travels towards the surface of water then, a large portion of the sound energy is reflected from the surface of the water and only a little bit fraction of sound energy(=0.1%) enters into the water suffering refraction.

2.What are the mechanical waves and electromagnetic waves? Give reason.

Answer: 

Those waves which required material medium to travel from one place to another are called the mechanical waves, such as sound waves rubber or rope under tension etc.
And Those waves are called the electromagnetic waves  which required no material medium to travel . They can travel even in the empty space. Such as light waves, radio waves, infrared and ultraviolet radiations etc. 

3.What are the transverse wave and the longitudinal waves ? 

Answer:
If the particles of the medium vibrate perpendicular to the direction of the propagation of the wave then those waves are called the transverse wave. A transverse wave has the crest and trough as shown below.

                   Trough                     Crest   


If the particles of the medium vibrate along the direction of the propagation of the waves then those waves are called the longitudinal waves. A longitudinal waves has the compression and rarefactions as shown below.

4.Longitudinal waves are called the pressure waves, Why?

Answer:

If the particles of the medium vibrate along the direction of the propagation of the waves, the waves are called the longitudinal waves. When they vibrate along the direction of the propagation of the waves they cause compression in the region in front of the vibrating particles and rarefaction to the backside. So, wherever they go, they create regions of high pressure and low pressure. So they are called the pressure waves.

5.Progressive wave:

Answer:

Progressive waves are those wave which carry the energy along with them while travelling from one place to another place. The energy transfer may occurs in the crest and trough or the compressions and the rarefactions. For examples: water waves, light waves, sound waves etc. 
                                                                                              3- Present position of the wave
                                                                                               2- position of wave before 3 
                                                                                               3- Position of wave before-2  

 













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