Question 41 : Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in
1. 4.2 seconds
2. 42 seconds
3. 4.2 years
4. 42 years
View Answer   Discuss with Members

Question 42 : One thousand microns is equal to
1. 10^-3m
2. 10^-6m
3. 10^-9m
4. 10^-12m
View Answer   Discuss with Members

Question 43 : Stars twinkle because
1. the intensity of light emitted by them changes with time
2. the distance of the stars from the earth changes with time
3. the refractive index of the different layers of the earth's atmosphere changes continuously[comma] consequently the position of the image of a start changes with time
4. the light from the star is scattered by the dust particles and air molecules in the earth's atmosphere
View Answer   Discuss with Members

Question 44 : It is easier to roll a stone up a sloping road than to lift it vertical upwards because
1. work done in rolling is more than in lifting
2. work done in lifting the stone is equal to rolling it
3. work done in both is same but the rate of doing work is less in rolling
4. work done in rolling a stone is less than in lifting it
View Answer   Discuss with Members

Question 45 : Minimum number of unequal vectors which can give zero resultant are
1. two
2. three
3. four
4. more than four
View Answer   Discuss with Members

Question 46 : Suitable impurities are added to a semiconductor depending on its use. This is done in order to
1. increase its life
2. enable it to withstand higher voltages
3. increase its electrical conductivity
4. increase its electrical resistivity
View Answer   Discuss with Members

Question 47 : It takes much longer to cook food in the hills than in the plains, because
1. in the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100^oC causing an increase in cooking time
2. due to low atmospheric pressure on the hills[comma] the water boils at a temperature higher than 100^oC and therefore water takes longer to boil
3. in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere
4. in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
View Answer   Discuss with Members

Question 48 : Stars appears to move from east to west because
1. all stars move from east to west
2. the earth rotates from west to east
3. the earth rotates from east to west
4. the background of the stars moves from west to east
View Answer   Discuss with Members

Question 49 : Planets do not twinkle because
1. they emit light of a constant intensity
2. their distance from the earth does not change with time
3. they are very far away from the earth resulting in decrease in intensity of light
4. they are nearer to earth and hence we receive a greater amount of light and[comma] therefore minor variations in the intensity are not noticeable
View Answer   Discuss with Members

Question 50 : Identify the vector quantity from the following
1. Heat
2. Angular momentum
3. Time
4. Work
View Answer   Discuss with Members