Range of Hearing and Ultrasound - UNSOLVED PRACTICE SET

Q7. Define infrasound and ultrasound. Give one animal that produces each type and explain how it uses that sound.

Q8. Why can dogs hear sounds that humans cannot? What does this tell us about the relationship between ear structure and frequency range?

Q9. Explain how bats use echolocation to navigate and catch prey in complete darkness. Why do bats use ultrasound rather than audible sound for this purpose?

Q10. What is ultrasonography? How is it used in medicine? Give two specific medical situations in India where ultrasonography is routinely used. 

Q11. Explain two industrial applications of ultrasound. For each, describe why high-frequency sound is more effective than ordinary sound in that application. 

Q12. Animals like elephants and whales are known to communicate using infrasound. What advantage does infrasound give them compared to audible sound for long-distance communication? Give one reason based on the properties of low-frequency sound.

Q13. Explain the range of hearing and the differences between infrasound, audible sound, and ultrasound. Your answer must include:
(a) the frequency range of each category,
(b) two examples of natural sources of each type,
(c) why humans can hear only within the 20–20,000 Hz range (relate to ear structure briefly),
(d) how the range of hearing changes with age in humans, and
(e) why CBSE textbooks note that children can generally hear higher frequencies than adults.

Q14. Describe in detail the applications of ultrasound in medicine and industry. Your answer should cover:
(a) how ultrasonography works (principle of reflection of ultrasound),
(b) at least three medical uses of ultrasound in Indian hospitals,
(c) at least two industrial uses (cleaning of instruments, detecting cracks in metal),
(d) why ultrasound is preferred over X-rays for certain medical scans, and
(e) one application of ultrasound that helps in navigation or detection of objects.

Q15. Write a detailed comparison of echolocation in bats and the SONAR technology used by ships and submarines. Your answer must cover:
(a) the principle behind both (reflection of ultrasound),
(b) how a bat detects the position, distance, and size of an insect,
(c) how SONAR sends a pulse and measures echo time to find depth,
(d) why both systems use ultrasound and not audible sound, and
(e) one limitation of echolocation in bats and one limitation of SONAR in submarines.

Q16. A bat emits ultrasonic pulses at a frequency of 50,000 Hz. The speed of ultrasound in air = 340 m/s.
(a) Calculate the wavelength of the bat's ultrasonic pulse.
(b) How does this wavelength compare to a sound at 500 Hz (audible, same speed)? Calculate the audible wavelength too.
(c) Smaller wavelengths can detect smaller objects. Based on your calculations, can the bat detect an insect of size 0.5 cm? Justify.

Q17. A doctor uses an ultrasound machine to scan a patient. The ultrasound pulse travels into the body at 1540 m/s and the echo from an internal organ returns in 0.00013 seconds.
(a) Calculate the total distance the ultrasound pulse travelled.
(b) Calculate the depth of the organ from the body surface.
(c) If another organ is at a depth of 12 cm, how long will the echo take to return?
(d) Why is the speed of ultrasound in body tissue (1540 m/s) much higher than in air (340 m/s)?

Q18. A submarine's SONAR emits a pulse and receives the echo from an underwater cliff after 8 seconds. Speed of sound in seawater = 1500 m/s.
(a) Calculate the distance of the cliff from the submarine.
(b) The submarine moves toward the cliff at 10 m/s for 60 seconds. How far is the cliff now?
(c) The SONAR pulses again. How long will the echo take this time?
(d) The submarine detects a school of fish — the echo returns in 0.4 seconds. How far away is the school of fish?