The sound from a mosquito is produced when it vibrates its wings at an
average rate of 500 vibrations per second. What is the time period of the
vibration?
Fill in the blanks with suitable words.
(a) Time taken by an object to complete one oscillation is called
__________.
(b) Loudness is determined by the __________ of vibration.
(c) The unit of frequency is __________
(d) Unwanted sound is called __________ .
(e) Shrillness of a sound is determined by the __________ of vibration.
In the following statements, tick ‘T’ against those which are true, and ‘F’
against those which are false.
(a) Sound cannot travel in vacuum. (T/F)
(b) The number of oscillations per second of a vibrating object is called
its time period. (T/F)
(c) If the amplitude of vibration is large, sound is feeble. (T/F)
(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F)
(e) The lower the frequency of vibration, the higher is the pitch. (T/F)
(f) Unwanted or unpleasant sound is termed as music. (T/F)
(g) Noise pollution may cause partial hearing impairment. (T/F)
Give reasons for
(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole.
(b) Intercellular spaces are absent in sclerenchymatous tissues.
(c) We get a crunchy and granular feeling, when we chew pear fruit.
(d) Branches of a tree move and bend freely in high wind velocity.
(e) It is difficult to pull out the husk of a coconut tree.
Describe the structure and function of different types of epithelial tissues. Draw diagram of each type of epithelial tissue.
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