Describe the construction of a kaleidoscope.
A simple device is used to obtain the colorful designs by multiple reflections is called kaleidoscope.
Principle: It works on the principle of multiple reflection of light.
Construction:
When seen through the hole, we will be able to see a variety of patterns in the tube.
Draw a labeled sketch of the human eye.
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.
Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
(a) Polished wooden table (b) Chalk powder
(c) Cardboard surface (d) Marble floor with water spread over it
(e) Mirror (f) Piece of paper
How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?
Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 16.19. Draw the reflected ray from the second mirror.
What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Explain how you can take care of your eyes.
State the laws of reflection.
Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teachers advise?
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.
What are the different ways in which water gets contaminated ?
Explain the importance of reproduction in organisms.
You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Explain why a charged body loses its charge if we touch it with our hand.
Differentiate between the following:
(a) Wildlife sanctuary and biosphere reserve
(b) Zoo and wildlife sanctuary
(c) Endangered and extinct species
(d) Flora and fauna
Write T against true and F against false in the following statements:
(a) Like charges attract each other (T/F)
(b) A charged glass rod attract a charged plastic straw (T/F)
(c) Lightning conductor cannot protect a building from lightning (T/F)
(d) Earthquakes can be predicted in advance (T/F)
Does pure water conduct electricity? If not, what can we do to make it conducting?
Name the petroleum product used for surfacing of roads.
Answer in brief:
(a) Why should we conserve biodiversity?
(b) Protected forests are also not completely safe for wild animals. Why?
(c) Some tribals depend on the jungle. How?
(d) What are the causes and consequences of deforestation?
(e) What is Red Data Book?
(f) What do you understand by the term migration?
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Find out the information about the national parks in your state. Identify and show their location on the outline map of India.