Important questions based on NCERT syllabus for Chapter 11 - Human Eye and Colourful World:
Question-1: A student has difficulty reading the blackboard while sitting in the last row. What could be the deffect? How can it be corrected?
Solution: 1. A student has difficulty in reading the blackboard while sitting in the last row. It shows that he is unable to see distant objects clearly. He is suffering from myopia.
2. This defect can be corrected by concave lens.
Question-2: Explain why planets do not twinkle at night.
Solution: 1. The planets are much closer to the earth, and are thus seen as extended sources.
2. If we consider a planet as a collection of a large number of point-sized sources of light, the total variation in the amount of light entering our eye from all the individual point-sized sources will average out to zero, thereby nullifying the twinkling effect.
Question-3: Why does the sun appear red at the time of sunset and sunrise? Explain.
Solution: 1. During sunset and sunrise, the sun is near horizon, and therefore the sunlight has to travel larger distance in atmosphere.
2. Due to this, most of the blue light (shorter wavelength) are scattered away by the particles.
3. The light of longer wavelength (red color) will reach our eye. This is why During the sunset and the sunrise, the color of the sun and its surrounding appears as red.