Class 10 Science - Chapter Light - Reflection and Refraction NCERT Solutions | A concave lens of focal length 15 cm for

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.

     Table 10.3 Absolute refractive index of some material media

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.

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.

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.

You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.

Define 1 dioptre of power of a lens.

Find the focal length of a lens of power – 2.0 D. What type of lens is this?

Find the focal length of a convex mirror whose radius of curvature is 32 cm.

The magnification produced by a plane mirror is +1. What does this mean?

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?

Use the data in Table 12.2 to answer the following –

(a) Which among iron and mercury is a better conductor?
(b) Which material is the best conductor?

What change will you observe if you test soap with litmus paper (red and blue)?

By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
Ga     Ge      As     Se     Be

At the time of short circuit, the current in the circuit

(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be –

(a) 1:2          (b) 2:1          (c) 1:4          (d) 4:1

How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?

How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

Draw a labelled diagram of the longitudinal section of a flower.

Give any two ways in which non-biodegradable substances would affect the environment.

Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V.