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11.

Assertion (A) Si and GaAs  are the preferred materials for solar cells

Reason (R)  Both these materials  have energy  band gaps much below the energy level corresponding to the maximum solar irradiance in the solar spectrum

The correct answer is

A) (A) is correct but (R) is incorrect

B) Both (A) and (R) are correct and (R0 is the correct explanation of (A)

C) Both (A) and (R) are correct. but (R0 is not the correct explanation of (A)

D) Both (A) and (R) are incorrect

12.

For the circuit shown in the figure, calculate the resistance between points A and B

A) 0.5 R

B) R

C) 15 R

D) $\frac{6}{5}R$

13.

A metal plate of thickness  2mm and area $36 \pi cm^{2}$ is slide into a parallel plate capacitor of plate spacing 6 mm and are $36 \pi cm^{2}$ . The metal plate is at a distance 3 mm from one of the plates. What is the capacitance of this arrangement?

$\left( Let\frac{1}{4 \pi \in_{0}}=9 \times 10^{9} Nm^{2}C^{-2}\right)$

A) 8 pF

B) 15 pF

C) 25pF

D) 20pF

14.

The limit of resolution of a telescope is $2.5 \times 10^{-7}$ rad. If the  telescope is used to detect light of wavelength  500 nm coming from a star, the diameter of the objective lens used by the telescope is

A) 244 cm

B) 258 cm

C) 228 cm

D) 264 cm

15.

A drone fitted with siren in flying directly away from the drone operator and towards a distant building at a speed of 15 m/s . The siren produces the sound of frequency 780Hz. What is the frequency that the  operator hears in the echo refected from the building,[ speed of sound is 340 m/s]

A) 766 Hz

B) 800 Hz

C) 816Hz

D) 840Hz

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