4.8 × 10-19Hz
9.3 × 10-7Hz
4.8 × 1014Hz
7.3 × 1014Hz
9.3 × 1014Hz
Correct answer is D
The work function (\(\phi\)) of a metal is defined as:
\(\phi = hf_0\)
\(f_0 = \frac{\phi}{h}\)
\(\phi = 3.0 eV = 3.0 \times 1.6 \times 10^{-19}\)
= \(4.8 \times 10^{-19} J\)
\(f_0 = \frac{4.8 \times 10^{-19}}{6.6 \times 10^{34}}\)
= \(0.727 \times 10^{15} s^{-1}\)
= \(7.27 \times 10^{14} s^{-1}\)
\(\approxeq 7.3 \times 10^{14} Hz\)
A lead-acid accumulator is used in preference to a dry battery in a car because
a dry battery cannot supply the necessary high voltage
a dry battery would not operate on a cold frosty morning
the accumulator can give a bigger current and can be recharged
the accumulator can supply a.c
the chemicals used in a dry battery constitute a fire hazard.
Correct answer is C
No explanation has been provided for this answer.
What gives rise to the line spectra observed in atoms?
change of an electron from a higher to a lower energy level in the atom
disturbed protons in the nucleus
excitation of an electron in the atom
kinetic energy of a moving atom
potential energy of an electron inside an atom
Correct answer is A
No explanation has been provided for this answer.
420 J
1680 J
1701 J
2100 J
3780 J
Correct answer is E
No explanation has been provided for this answer.
6.0cm
12.0cm
18.0cm
24.0cm
48.0cm
Correct answer is A
No explanation has been provided for this answer.