Class 8 Science - Chapter Sound NCERT Solutions | Which of the following voices is likely

Sketch larynx and explain its function in your own words.

Explain in what way noise pollution is harmful to humans.

List sources of noise pollution in your surroundings.

Your parents are going to buy a house. They have been offered one on the roadside and another three lanes away from the roadside. Which house would you suggest your parents should buy? Explain your answer.

Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain?

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.

Identify the part which vibrates to produce sound in the following instruments:
(a) Dholak (b) Sitar (c) Flute

A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.

What is the difference between noise and music? Can music become noise sometimes?

Choose the correct answer :
Sound can travel through
(a) gases only (b) solids only
(c) liquids only (d) solids, liquids and gases.

Which of the following can be beaten into thin sheets?
  (a) Zinc     (b) Phosphorus     (c) Sulphur     (d) Oxygen

Fill in the blanks
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the terminal of the battery.
(d) The process of depositing a layer ofany desired metal on another material by means of electricity is called .

Give two examples each of situations in which you push or pull to change the state of motion of objects.

Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces.                                                                                                                                                                      (c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.

List conditions under which combustion can take place.

Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)

Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.

Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called                  .
(b) Species found only in a particular area is known as                          .
(c) Migratory birds fly to far away places because of                     changes.

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.

What are the different ways in which water gets contaminated ?

Angle of incidence is equal to the angle of reflection
(a) Always (b) Sometimes
(c) Under special conditions (d) Never

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Indicate whether the following statements are True (T) or False (F):
(a) Oviparous animals give birth to young ones.                                    ( )
(b) Each sperm is a single cell.                                                              ( )
(c) External fertilization takes place in frog.                                           ( )
(d) A new human individual develops from a cell called gamete.          ( )
(e) Egg laid after fertilization is made up of a single cell.                       ( )
(f) Amoeba reproduces by budding.                                                       ( )
(g) Fertilization is necessary even in asexual reproduction.                  ( )
(h) Binary fission is a method of asexual reproduction.                         ( )
(i) A zygote is formed as a result of fertilization.                                    ( )
(j) An embryo is made up of a single cell.                                              ( )

Explain circumstances leading to acid rain. How does acid rain affect us?

Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.

Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.20. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?

Describe the ‘Green House Effect’ in your own words.

You are a member of the municipal body of your town.

Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

At an individual level, how can you help reduce air pollution?