Q15 of 58 Page 1

Name the type of mirror used (i) by dentists and (it) in solar furnaces. Give two reasons why such mirrors are used in each case.

(i) The mirror used by dentists is Concave mirror so that large images of teeth can be seen because concave mirror forms an enlarged image of the tooth and it is easy to locate the defect in the teeth.


(ii) Concave mirrors are used in solar furnaces as they are used as reflectors in solar furnaces. Concave mirrors helps in focusing the sun’s heat rays on the furnace. As a result, the solar furnace becomes very hot.


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13

Explain with the help of suitable examples why certain traits cannot be passed on to the next generation? What are such traits called?

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A cross was carried out between a pure bred tall pea plant and a pure bred dwarf pea plant and F1 progeny was obtained. Later, the F1 progeny was salted to obtain F2 progeny. Answer the following questions:(a) What is the phenotype of the F1progeny andwhy?

(b) Give the phenotypic ratio of theF2 progeny.


(c) Why is the F2 progeny different from the F1 progeny?

 16

An object is placed on a metre scale at 8 cm mark was focused on a white screen placed at 92 cm mark, using a converging lens placed on the scale at 50 cm mark.

(i)Find the focal length of the converging lens.


(ii)Find the position of the image formed if the object is shifted towards the lens at a position of 29.0 cm.


(iii)State the nature of the image formed if the object is further shifted towards the lens.

 17

When and where do we see a rainbow? How is a rainbow formed? Draw a labelled diagram to illustrate the formation of a rainbow.