Que. 3) Answer the following questions (Any Five)
(15)
the
i) What is meant by radioactivity ?
ii) Why methane is called marsh gas?
iii) Where and why are sound absorbing materials used?
iv) A canvex mirror has a focal length of 18 cm. The image of an object kept
in front of the mirror is half the height of the object. What is the distance of
object from the mirror.
What is an echo? What factors are important to get a distinct echo ?
vi) Explain use of CO2 in fire extinguisher.
vii) Write the harmful effects of “Artificial dye".
viii)Explain properties of carbon.
Que 4) Solve the following questions. (Any One)
(5)
i) Which type of mirrors are used in the following
Answers
Answer:
we use concave mirror
In car,motorcycle convex mirror
Answer:
As its name implies, radioactivity is the act of emitting radiation spontaneously. This is done by an atomic nucleus that, for some reason, is unstable; it "wants" to give up some energy in order to shift to a more stable configuration
Methane is called marsh gas because methane is found in marshy land.It is found in marshy land because when organism decomposes they produce methane.
The sound absorbing materials are used on the roofs and walls of auditoriums, concert halls, theatres, etc. as well as upholsteries choosen for these rooms are made of sound absorbing materials. In these places, excessive reverberation is highly undesirable
Carbon dioxide extinguishes work by displacing oxygen, or taking away the oxygen element of the fire triangle. The carbon dioxide is also very cold as it comes out of the extinguisher, so it cools the fuel as well.
The physical and chemical properties of carbon depend on the crystalline structure of the element. Its density fluctuates from 2.25 g/cm³ (1.30 ounces/in³) for graphite and 3.51 g/cm³ (2.03 ounces/in³) for diamond. The melting point of graphite is 3500ºC (6332ºF) and the extrapolated boiling point is 4830ºC (8726ºF).
Explanation: