refraction n dispersion of light

REFRACTION AND DISPERSION OF LIGHT

ASSIGNMENT-2

CLASS-VIII

Q1. Who discovered that sunlight consists of 7 colours?

Q2. Why sunlight reaches us (earth) in the form of white light and not as its components?           

Q3. A laser beam consists of light of only single colour. Will a laser beam incident on a glass prism produce a spectrum?

Q4. A glass slab doesn’t show dispersion. Why?

Q5. A rainbow is seen in the sky after rainfall. Why?

Q6. Name the lens which has a virtual focus.

Q7. How many focus points does a concave or a convex lens have?

Q8. Name the lens which always forms a virtual and erect image, no matter where the object is placed.

Q9. Name the phenomenon on which working of lens is based.

Q10. What is the difference between a convex lens and a concave lens?

Q11. Which lens is present in the eye-- concave or convex?

Q12. The image of a candle is formed by a convex lens. If the lower half of the lens is covered with a black paper, will still the full image of the candle be formed on the screen? Explain by drawing a suitable ray diagram.

Q13. When a magnifying glass focuses the sun’s rays on a sheet of paper, it starts burning. Why?

Q14. Which of the following would you prefer to read very small letters printed on the pages of a dictionary?

i)                   A convex lens of focal length 100cm

ii)                 A concave lens of focal length 10cm

iii)               A concave lens of focal length 5cm

iv)               A convex lens of focal length 5cm

Q15. You are given a convex lens and a black paper. A teacher asks you to burn the paper in sunlight. Draw the ray diagram to show that paper burns in sunlight.