17. Which object possesses the greatest tendency to create a loud sound?
a. Birds
b. cellphone
c.jet plane
d. vehicle

18. Which of the following characteristics that affects the pitch of sound waves?
a. Amplitude
b. frequency
C. quality
d. wavelength

19. Which statement is true about how loudness of sound varies with the person?
a. A very loud sound may destroy eardrums
b. Loud and soft sounds depend upon the source of sound
C. A rock music may be pleasant to a teenager but unpleasant to an old lady
d. A loud sound is created by a large energy carried by the sound wave

20. How can we identify the voice of our mother even without seeing her?
a. Mother always talks that makes us remember their voice.
b. The voice of our mother has a high pitch that makes it easy to recognize.
c. Our mother creates a very loud sound that enables us to easily identify her voice
d. The voice of our mother has its distinct characteristics that distinguishes her voice from
others,

21. What type of sound waves do whale produced to communicate with each other deep in the
ocean?
a. Audible sound
b. infrasonic sound
c. ultrasonic sound
d. unpleasant sound

22. Why is it important for humans to protect the ear against very intense or loud sound?
a. The human ears have certain limit that can withstand only certain intensity of sound
b. Loud sound can create permanent damage to the nerves in the ear
C. The loud sound may cause some brain damage
d. All of the above

23. Which of the following is a luminous object?
a. Headlight b. mirror
c. planet
d. rock

24. A ray of light travels from the source to the object. What is the direction of its path?
a. Curve
b. parallel
c. opposite
d. straight

25. Which of the following proves that light travels in a straight line?
a. Eclipses
b. shadows
c. mirror images
d. all of these

26. What method of heat transfer is involved when you cook your food using a cooking pan?
a. Conduction b. convection
c. induction
d. radiation

27. What do you call the ability of objects to conduct heat?
a. Absorption
b. conductivity
c. malleability
d. refection

28. Why do different materials conduct heat differently?
a. Materials have different conductivity
c. materials have different atoms
b. Materials have different characteristics
d. materials have different mass

29. Why does convection happen in fluids?
a. The particles in fluid help in absorbing energy from environment
b. The particles in fluid can easily flow that enables it to transfer energy
C. Fluid has no definite shape but has a volume
d. Fluid can make a material float in it

30. Method of heat transfer that occurs through empty space is called
a. Conductor b. radiation
C. conduction
d. convection​