**21. **Rainbow formation is a natural phenomenon illustrating that white light

**A.**splits into three components after rainfall**B.**is dispersed by glass prisms**C.**splits into its constituent colours before rainfall**D.**is dispersed into its constituent colours after rainfall

**Correct Option: Answer is D**

**22. **

The lens illustrated above can best be described as a

**A.**converging meniscus**B.**plano-convex**C.**diverging meniscus**D.**bi-convex

**Correct Option: Answer is B**

The diagram is that of a plano-convex lens; a type of converging lens

**23. **Two plane mirrors are inclined to each other such that an object placed between them has 11 images. Determine the angle of inclination

**A.**30°**B.**45°**C.**60°**D.**90°

**Correct Option: Answer is A**

Formula for number of images = \(\frac{360}{n} – 1\)

where n is the angle of inclination.

Given the number of images = 11, we have

\(\frac{360}{n} – 1 = 11\)

\(\frac{360}{n} = 12\)

\(n = \frac{360}{12} =30°\)

**24. **The pitch of a note is not affected by

**A.**frequency**B.**tension in a vibrating string**C.**mass of a vibrating string**D.**amplitude of sound wave

**Correct Option: Answer is D**

**25. **When two flat plate conductors are arranged in such a way that they possess equal and opposite charges seperated by a dielectric, they form a/an

**A.**electroscope**B.**electrophorus**C.**capacitor**D.**cell

**Correct Option: Answer is C**

Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium.

**26.**

Which electrical device is illustrated above?

**A.**a.c. generator**B.**a.c. motor**C.**d.c. generator**D.**d.c. motor

**Correct Option: Answer is C**

**27. **A simple barometer is constructed using a liquid Q1 of density 16.2g/cm³. Calculate the least lenth of the tube to be used to measure pressure of 1.5atm. [Density of mercury = 13.6g/cm³, 1atm = 76.0 cm of Mercury]

**A.**1358mm**B.**957mm**C.**760mm**D.**638mm

**Correct Option: Answer is D**

Let \(h_{Q}\) and \(\rho_{Q}\) be the least length and the density of \(Q_{1}\)

while \(h\) and \(\rho\) are the length and density of mercury respectively.

\(h\times \rho \times g = h_{Q} \times \rho_{Q} \times g\)

\(76cm \times 13.6 \times 10 = h_{Q} \times 16.2 \times 10\)

\(h_{Q} = \frac{76\times13.6\times10}{16.2\times10}\)

\(h_{Q} = \frac{10336}{162}\)

\(h_{Q} \approxeq 63.8cm = 638mm\)

**28. **

The diagram above illustrates the mercury-in-glass thermometer used for determining the temperature of a room. Use the data on it to determine the room temperature.

**A.**3.3°C**B.**7.0°C**C.**13°C**D.**30.0°C

**Correct Option: Answer is C**

**29. **To obtain a virtual, erect and magnified image from a thin converging lens, an object must be placed

**A.**between the focus and the lens**B.**at the focus**C.**between the focal length and twice the focal length**D.**beyond twice the focal length

**Correct Option: Answer is A**

When the object is placed between the optical centre of the lens and the focal length, the image formed is virtual, erect and magnified.

**30. **

The diagram above represents a transverse travelling wave. Which two points are 180° out of phase?

**A.**A and E**B.**B and D**C.**C and F**D.**D and H