# If the diameter of a carbon atom is 0.15 nm, the number of carbon atoms that can be placed side by side in a straight line across the length of the scale of length 20 cm long will be: 1. 1.33 × 107 2. 5.46 × 108 3. 1.33 × 109 4. 2.36 × 108 

Subtopic:  Introduction of Atomic Structure |
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The charge on the oil drop is –1.282 × 10–18C. The number of electrons present in it would be :

1. 15

2. 8

3. 2

4. 6

Subtopic:  Number of Electron, Proton & Neutron |
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An element with a mass number of 81 contains 31.7% more neutrons as compared to protons. The atomic symbol of the element would be

$1.$ ${}_{35}{}^{81}\mathrm{Br}$
$2.$ ${}_{36}{}^{81}\mathrm{Br}$
$3.$ ${}_{35}{}^{79}\mathrm{Br}$
$4.$ ${}_{36}{}^{79}\mathrm{Br}$

Subtopic:  Number of Electron, Proton & Neutron |
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An ion with a mass number of 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. The symbol of the ion is -

$1.$ ${}_{26}{}^{56}\mathrm{Fe}^{+3}$
$2.$ ${}_{26}{}^{57}\mathrm{Fe}^{+3}$
$3.$ ${}_{27}{}^{58}\mathrm{Fe}^{+3}$
$4.$ ${}_{25}{}^{56}\mathrm{Fe}^{+3}$

Subtopic:  Number of Electron, Proton & Neutron |
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A nitrogen laser produces radiation at a wavelength of 337.1 nm. If the number of photons emitted is
5.6 × 10
24, the power of the laser is:

$1.$ $4.56$ $×$ ${10}^{7}$ $\mathrm{J}$
$2.$ $3.33$ $×$ ${10}^{6}$ $\mathrm{J}$
$3.$ $1.29$ $×$ ${10}^{6}$ $\mathrm{J}$
$4.$ $9.17$ $×$ ${10}^{5}$ $\mathrm{J}$

Subtopic:  Planck's Theory |
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If the photon detector receives a total of 3.15$×{10}^{-18}$ J from the radiation of 600 nm,
the number of photons received by the detector would be:

$1.$ ${10}^{2}$
$2.$ $10$
$3.$ $50$
$4.$ $20$

Subtopic:  Planck's Theory |
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A radiation source emitted  2.5 × 1015 photons in 2 nanoseconds. Energy of the source is -

$1.$ $8.28$ $×$ ${10}^{-10}$ $\mathrm{J}$
$2.$ $8.24$ $×$ ${10}^{10}$ $\mathrm{J}$
$3.$ $7.12$ $×$ ${10}^{-11}$ $\mathrm{J}$
$4.$ $2.12$ $×$ ${10}^{}$ $10$ $\mathrm{J}$

Subtopic:  Planck's Theory |
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Emission transitions in the Paschen series end at orbit n = 3 and start from orbit n and can be represented as v = 3.29 × 1015 (Hz)$\left(\frac{1}{{3}^{2}}-\right)$ $\frac{1}{{\mathrm{n}}^{2}}$The value of n if the transition is observed at 1285 nm is :

 1 6 2 5 3 8 4 9

Subtopic:  Hydrogen Spectra |
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If the velocity of the electron is 1.6 × 106 ${\mathrm{ms}}^{-1}$. The de Broglie wavelength associated with this electron is:

$1.$ $590$ $\mathrm{pm}$
$2.$ $455$ $\mathrm{pm}$
$3.$ $512$ $\mathrm{pm}$
$4.$ $401$ $\mathrm{pm}$

Subtopic:  De Broglie Equation |
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The characteristic velocity associated with a neutron that has a wavelength of 800 pm is :

 1 496 m s-1 2 567 m s-1 3 494 cm s-1 4 501 m s-1
Subtopic:  De Broglie Equation |
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