Find the focal length of a convex mirror whose radius of curvature is 32 cm.
Given:
Radius of curvature, R = 32 cm
Radius of curvature = 2 × Focal length (f)
R = 2f
On putting the values we get
Therefore, the focal length of the given convex mirror is 16 cm.
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
Table 10.3 Absolute refractive index of some material media
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
Define 1 dioptre of power of a lens.
The magnification produced by a plane mirror is +1. What does this mean?
Find the focal length of a lens of power – 2.0 D. What type of lens is this?
Name the type of mirror used in the following situations.
(a) Headlights of a car.
(b) Side/rear-view mirror of a vehicle.
(c) Solar furnace.
Support your answer with reason.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Name two metals which are found in nature in the free state.
Five solutions A,B,C,D and E when tested with universal indicator showed pH as 4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Why are traits acquired during the life-time of an individual not inherited?
How can you as an individual contribute or make a difference to the management of (a) forests and wildlife, (b) water resources and (c) coal and petroleum?
What is the role of the acid in our stomach?
What is the principle of an electric motor?
Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
What are alloys?
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?