1st Year Physics Chapter 8 Notes

• Important 1st year physics chapter 8 mcqs from Punjab Textbook.
• Waves: Waves transport energy without transporting matter. The energy transportation is carried by a disturbance, which spreads out from a source. We are well familiar with different types of waves such as water waves in the ocean, or gently formed ripples on a still pond due to rain drop. When a musician plucks a guitar-string, sound waves are generated which on reaching our ear, produce the sensation of music. Wave disturbances may also come in a concentrated bundle like the shock waves from an aeroplane flying at supersonic speed. Whatever may be the nature of waves, the mechanism by which it transports energy is the same. A succession of oscillatory motions are always involved. The wave is generated by an oscillation in the vibrating body and propagation of wave through space is by means of oscillations. The waves which propagate by the oscillation of material particles are known as mechanical waves
• There is another class of waves which, instead of material particles, propagate out in space due to oscillations of electric and magnetic fields. Such waves are known as electromagnetic waves. We will undertake the study of electromagnetic waves at a later stage Here we will consider the mechanical waves only. The waves generated in ropes, strings, coil of springs, water and air are all mechanical waves. So far we have been considering motion of individual particles but in case of mechanical waves, we study the collective motion of particies. An example will help us here. If you look at a black and white picture in a newspaper with a magnifying glass, you will discover that the picture is made up of many closely spaced dots. If you do not use the magnifier, you do not see the dots. What you see is the collective effect of dots in the form of a picture. Thus what we see as mechanical wave is actually the effect of oscillations of a very large number of particles of the medium through which the wave is passing.
• Progressive waves
• Transverse and longitudinal waves
• Transverse periodic waves
• Periodic waves
• Important 1st year physics chapter 8 solved exercise from Punjab Textbook.
• Phase relationship between two points on a wave
• Longitudinal periodic waves
• The speed of sound in air
• Important 1st year physics chapter 8 important long questions from Punjab Textbook.
• Effect of variation of pressure, density, and temperature on the speed of sound in a gas: 1. Effect of Pressure:
• Since density is proportional to the pressure, the speed of sound is not affected by a variation in the pressure of the gas
• 2. Effect of Density: At the same temperature and pressure for the gases having the same value of 7, the speed is inversely proportional to the square root of their densities Eq. 8.7. Thus the speed of sound in hydrogen is four times its speed in oxygen as density of oxygen is 16 times that of hydrogen.
• 3. Effect of Temperature: When a gas is heated at constant pressure, its volume is increased and hence its density is decreased. 
• Principle of superposition
• Interference
• Beats
• Important 1st year physics chapter 8 long questions from Punjab Textbook.
• Reflection of waves
• Stationary waves
• Stationary waves in a stretched string
• Stationary waves in air columns
• Doppler effect
• Important 1st year physics chapter 8 numericals from Punjab Textbook.
• Applications of the Doppler Effect