1
TS EAMCET 2020 (Online) 14th September Evening Shift
MCQ (Single Correct Answer)
+1
-0

The radiation energy emitted per second by a point source is 100 W . If the efficiency of the source is $4 \%$, then the rms value of the electric field at distance of 2 m is [use $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9$ in SI unit]

A

$\sqrt{60} \mathrm{~V} / \mathrm{m}$

B

$\sqrt{30} \mathrm{~V} / \mathrm{m}$

C

$\sqrt{50} \mathrm{~V} / \mathrm{m}$

D

$\sqrt{40} \mathrm{~V} / \mathrm{m}$

2
TS EAMCET 2020 (Online) 14th September Evening Shift
MCQ (Single Correct Answer)
+1
-0

A light of wavelength 310 nm is used in a photoelectric experiment. The metal electrode of work function of 2.5 eV is used in the experiment. The stopping potential for the photoelectrons will be (assume, $h c=1240 \mathrm{eV}-\mathrm{nm}$ )

A

1.0 V

B

1.5 V

C

2.0 V

D

2.5 V

3
TS EAMCET 2020 (Online) 14th September Evening Shift
MCQ (Single Correct Answer)
+1
-0

If the first line in the Lyman series has wavelength $\lambda$, then the first line in Balmer series has the wavelength

A

$\frac{27}{5} \lambda$

B

$\frac{32}{27} \lambda$

C

$\frac{28}{21} \lambda$

D

$\frac{15}{4} \lambda$

4
TS EAMCET 2020 (Online) 14th September Evening Shift
MCQ (Single Correct Answer)
+1
-0

The half-life of a radiocative isotope is 30 h . How long will it take to get reduced to $12.5 \%$ of its initial amount?

A

120 h

B

90 h

C

60 h

D

50 h

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