Q22 of 38 Page 1

What is the difference in colours of the sun observed during sunrise/sunset and noon? Give explanation for each.

During sunrise/sunset it appears red as light has to travel a long distance from the sun through the atmosphere to reach the eye of the observer. Red light is scattered least due to its long wavelength than blue light hence it appears red to the observer.


But at noon it appears white as the sun is directly over our head and light rays have to travel short distances without much scattering of any particular the colour of light. Hence it appears white.


More from this chapter

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21

(a) How does speciation take place?

(b) Define the term GENE.


(c) The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a child if he inherits a gene for red colour from his mother and a gene for black hair from his father? Express with the help of flow chart.

 22

Explain the formation of rainbow in the sky with the help of a diagram. List the three phenomena of light involved. Which colour – violet or red appears at top of the rainbow?

 23

(i) Which property of concave mirror is utilized for using them as shaving mirrors?

(ii) Light passes through a rectangular glass slab and through a triangular glass prism. Using proper ray diagram, explain in what way does the direction of the two emergent beams differs with respect to the incident beam of light.


(iii) A concave lens has a focal length of 50 cm Calculate its power.

 24

(i) Rohit claims to have obtained an image twice the size of object with a concave lens. Is he correct? Give reason for your answer.

(ii) Where should an object be placed in case of a convex lens to form an image of same size as of the object? Show with the help of ray diagram the position and the nature of the image formed.


(iii) With the help of ray diagram, illustrate the change in position, nature and size of the image formed if the convex lens in case of (ii) is replaced by concave lens of same focal length.