## The Human Eye and the Colourful World – Unit Test Paper

Q1: A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power which type?

Q2: Give reasons for the following:
i. Stars twinkle at night.
ii. The sun appears reddish early in morning.
iii. Planets do not twinkle.
iv. Red colour is used in danger signals.

Q3: A person walking in desert gets a illusion of seeing water. Name the phenomenon of light responsible for it.

Q4: Distinguish between Refraction and Dispersion.

Q5: Explain how formation of rainbow occurs alongwith suitable diagram.

Q6: Explain apparent star position along with suitable diagram.

Q7: What is the speed of light in diamond if absolute refractive index of diamond is 2.4 and velocity of light in vacuum is 3 × 10⁸ m/s ?

Q8:  Why is the colour of the clear Sky Blue?

Q9: Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.

Q10: Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Q11: A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.

Q12: Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence define the angle of deviation.