Class 11 Physics Ch 8 Notes

• Important class 11 physics ch 8 exercise solutions from Punjab Textbook.
• Differentiate between mechanical waves and electromagnetic waves.
• Differentiate between longitudinal waves and transverse waves: Ans: Longitudinal waves Transverse waves • The waves in which the particles of the medium move back and forth along the direction of propagation of wave is called the longitudinal waves. • For example, Sound waves, Waves produced in slinky. • The waves in which the vibratory motion of particles of the medium is perpendicular to the direction of waves is called transverse waves • For example, Water waves, string waves and waves produced in slink.
• Why did Newton’s fail to calculate the velocity of sound accurately?
• What are the effects of pressure and density on speed of sound?
• Why sound travel faster in hydrogen than in oxygen?
• What is effect of temperature on the speed of sound?
• State the principle of super position. What are its different cases?
• Important class 11 physics ch 8 question answer from Punjab Textbook.
• Define interference. What is constructive and destructive interference?
• What is path difference? What should be the path difference for construction and destructive interference?
• What are beats? Write its formula and uses: Ans: Beats: When two waves of slightly different frequencies, travelling in the same direction overlap each other then there is a periodic variation of sound between maximum and minimum loudness called beats. Beats frequency: Number of beats per second is equal to the difference between frequencies of turning forks.
• What is effect on phase of a wave when it is reflected from (i) rare medium (ii) denser medium
• Important class 11 physics ch 8 numericals from Punjab Textbook.
• What are stationary waves? How are they produced?: Ans: Stationary Wave: The resultant wave produced by the superposition of two identical waves travelling in opposite direction is called stationary wave. Production of Stationary Waves: Two waves of same frequency travelling in opposite direction produce stationary waves.
• On what factors does the fundamental frequency in a stretched string depends?
• Which is richer in harmonics? An open organ pipe or a closed organ pipe?
• Define Doppler’s effect. Give its example.
• Define Doppler shift. Write down its formula.
• What do you mean by red shift and blue shift?
• Write the applications of Doppler’s effect.
• What features do longitudinal waves have common with transverse waves?
• The five possible waveforms obtained, When the output form from a microphone is fed into the Yinput of cathode ray of oscilloscope, with the times base on, are shown in fig. These waveforms obtained under the same adjustment of the cathode ray of oscilloscope controls. Indicate the waveform. (a) Which trace represents the loudest note? (b) Which trace represents the highest frequency?
• Explain the terms, crest, node and antinode: Ans: Crest: "The portion of the transverse wave above the mean position is called crest." Trough: "The portion of the transverse wave below the mean position is called trough." Node: "The points on the stationary wave which show zero displacement permanently are called nodes." 
• Why does sound travel faster in solids than in gases?
• How are beats useful in tuning musical instrument?
• As a result of a distant explosion, an observer senses a ground tremor and then hears the explosion. Explain the time difference.
• Explain why sound travels faster in warm air than in cold air. 
• How should a sound move with respect to an observer so that frequency of its sound does not change?