NEET Physics: Questions 1376 - 1380 of 2099

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Question number: 1376

» Properties of Solids & Liquids » Newton's Law of Cooling

MCQ▾

Question

A body initially at 80° C cools to 64° C in 5 minutes and to 52° C in 10 minutes. The temperature of the body after 15 minutes will be

Choices

Choice (4) Response
a.

42.7° C

b.

47°

c.

40° C

d.

35° C

Question number: 1377

» Properties of Solids & Liquids » Elastic Behavior

MCQ▾

Question

The lengths and radii of two wires of same material are respectively L, 2L, and 2R, R. Equal weights are applied on then. If the elongations produced in them are l 1 and l 2 respectively then their ratio will be

Choices

Choice (4) Response
a.

4: 1

b.

2: 1

c.

8: 1

d.

1: 8

Question number: 1378

» Properties of Solids & Liquids » Heat Transfer » Conduction

MCQ▾

Question

A 5 cm thick ice block is there on the surface of water in a lake. The temperature of air is - 10° C; how much time it will take to double the thickness of the block (L = 80 cal/g, K ice = 0.004 erg/s-k, d ice = 0.92 g cm -3)

Choices

Choice (4) Response
a.

191 hours

b.

1 hour

c.

1.91 hours

d.

19.1 hours

Question number: 1379

» Dual Nature of Matter and Radiation » Particle Nature of Light

MCQ▾

Question

In a photo-emissive cell with exciting wavelength λ, the fastest electron has speed V. If the exciting wavelength is changed to 3λ4 , the speed of the fastest emitted electron will be

Choices

Choice (4) Response
a.

v(34)12

b.

Greaterthanv(43)12

c.

Lessthanv(43)12

d.

v(43)12

Question number: 1380

» Dual Nature of Matter and Radiation » Einstein's Photoelectric Equation

MCQ▾

Question

Electrons are accelerated in television tubes through potential difference of about 10 KV

(1) The lowest wavelength of the emitted X-rays is 12.4A

(2) The lowest wavelength of the emitted X-rays is 1.24 A

(3) The highest frequency of the emitted X-rays is 2.4 × 10 8 Hz

(4) The highest frequency of the emitted X-rays is 2.4 × l0 18 Hz

Select the correct answers and mark it according to the following codes:

Choices

Choice (4) Response
a.

1, 2 and 3 are correct

b.

2 and 4 are correct

c.

1 and 2 are correct

d.

1 and 3 are correct

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