Atoms Test

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Atoms Test - 38

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Weekly Quiz Competition

Question 1
1 / -0

An element X has number of protons = 4. What will be its mass number if it has 3 neutrons?

A
4

B
3

C
7

D
5

Solution

Mass number of any element is equal to sum of number of neutron and number of proton.
Question 2
1 / -0

The radius of hydrogen atom in the first excited level is

A
twice

B
four times

C
same

D
half

Solution
Question 3
1 / -0

Fraunh offer line of the solar system is an example of:

A
line absorption specturm

B
emission of line system

C
line emission spectrum

D
emission of band spectrum

Solution

Fraunhoffer line in the spectrum of solar system arises due to absorption of certain wavelength of sun rays coming from the core. While passing through the outer region, which is at low temperature, certain wavelengths are absorbed which results in dark lines in the spectrum.
Question 4
1 / -0

In a hydrogen atom, the electron is making $$6.6\times 10^{15} revs^{-1}$$ around the nucleus in an orbit of radius $$0.528 \overset{o}{A}$$. The magnetic moment $$(A-m^2)$$ will be.

A
$$1\times 10^{-15}$$

B
$$1\times 10^{-10}$$

C
$$1\times 10^{-23}$$

D
$$1\times 10^{-27}$$

Solution

Current, $$I=6.6\times 10^{15}\times 1.6\times 10^{-19}$$
$$=10.5\times 10^{-4}A$$.
Area $$A=\pi R^2=3.142\times (0.528)^2\times 10^{-20}m^2$$
so, Magnetic moment
$$M=IA=10.5\times 10^{-4}\times 3.142\times (0.528)^2\times 10^{-2}$$
$$=10\times 10^{-24}=10^{-23}$$ units
Question 5
1 / -0

If an electron is revolving around the hydrogen nucleus at a distance of $$0.1$$nm, what should be its speed?

A
$$2.188\times 10^6 ms^{-1}$$

B
$$1.094\times 10^6 ms^{-1}$$

C
$$4.376\times 10^6 ms^{-1}$$

D
$$1.59\times 10^6 ms^{-1}$$

Solution

electrostatic force=centripetal force
$$\displaystyle\frac{1}{4\pi \varepsilon_0}\frac{Ze^2}{r^2}=\frac{mv^2}{r}$$
$$\therefore v=\sqrt{\left(\displaystyle\frac{1}{4\pi \varepsilon_0}\frac{Ze^2}{mr}\right)}$$
$$=\sqrt{\displaystyle\frac{9\times 10^9\times 1\times (1.6\times 10^{-19})^2}{(9.1\times 10^{-31})\times (0.1\times 10^{-9})}} =1.59\times 10^6ms^{-1}$$
Question 6
1 / -0

Which of the following is not an inherent property of the photons?

A
Momentum

B
Energy

C
Charge

D
Velocity

Solution

A photon is a particle which has zero charge and zero mass and is denoted by $$\gamma$$. The energy of photon is
$$E = hv$$
Here, $$v =$$ frequency and $$h =$$ Planck's constant.
The momentum of the photon is $${h}/{v}$$ and its velocity is the velocity of light $$\left(c\right)$$.
So, the charge is not the property of photons.
Question 7
1 / -0

The angular speed $$(\omega)$$ of an electron revolving in $$n^{th}$$ Bohr orbit and corresponding principal quantum number(n) are related as ____________.

A
$$\omega\propto n^3$$

B
$$\omega\propto\dfrac{1}{ n^3}$$

C
$$\omega\propto n^2$$

D
$$\omega\propto\dfrac{1}{ n^2}$$

Solution

Bohr's Model gives the following conclusions,
$$v\propto\dfrac{1}{n}$$
$$\Rightarrow r\propto{n^2}$$
$$\Rightarrow \omega \propto \dfrac vr \propto \dfrac {1}{n^3}$$
Question 8
1 / -0

If a cathode ray tube has a potential difference $$V$$ volt between the cathode and anode, then the speed $$v$$ of cathode rays is given by:

A
$$v\propto { V }^{ 2 }$$

B
$$v\propto \sqrt { V } $$

C
$$v\propto \cfrac { 1 }{ V } $$

D
$$v\propto V$$

Solution

$$qV=\cfrac { 1 }{ 2 } m{ v }^{ 2 }$$
or $$v=\sqrt { \cfrac { 2qV }{ m } } $$
ie $$v\propto \sqrt { V } $$
Question 9
1 / -0

For the Paschen series the values of $${ n }_{ 1 }$$ and $${ n }_{ 2 }$$ in the expression $$\Delta E=Rhc\left( \dfrac { 1 }{ { n }_{ 1 }^{ 2 } } -\dfrac { 1 }{ { n }_{ 2 }^{ 2 } } \right) $$ are

A
$${ n }_{ 1 }=1,{ n }_{ 2 }=2,3,4,\dots $$

B
$${ n }_{ 1 }=2,{ n }_{ 2 }=3,4,5,\dots $$

C
$${ n }_{ 1 }=3,{ n }_{ 2 }=4,5,6,\dots $$

D
$${ n }_{ 1 }=4,{ n }_{ 2 }=5,6,7,\dots $$

Solution

Paschen series is the third series of hydrogen spectrum and lies in the infrared region, therefore for this series, $${ n }_{ 1 }=3$$ and $${ n }_{ 2 }>{ n }_{ 1 }$$, ie, $$4,5,6,\dots $$
Question 10
1 / -0

The spectrum obtained from the chromosphere of the sun at the time of total solar eclipse is :

A
line emission spectrum

B
band emission spectrum

C
continuous emission spectrum

D
line absorption spectrum

Solution

The spectrum obtained is the line emission spectrum of $${ D }_{ 3 }$$ line of neutral helium at $$5876 \mathring{A}$$ wavelength (almost yellow colour).

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Re-Attempt Weekly Quiz Competition

Atoms Test - 38

Result

Atoms Test - 38

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SHARING IS CARING

Question 1

4

3

7

5

Solution

Question 2

twice

four times

same

half

Solution

Question 3

line absorption specturm

emission of line system

line emission spectrum

emission of band spectrum

Solution

Question 4

$$1\times 10^{-15}$$

$$1\times 10^{-10}$$

$$1\times 10^{-23}$$

$$1\times 10^{-27}$$

Solution

Question 5

$$2.188\times 10^6 ms^{-1}$$

$$1.094\times 10^6 ms^{-1}$$

$$4.376\times 10^6 ms^{-1}$$

$$1.59\times 10^6 ms^{-1}$$

Solution

Question 6

Momentum

Energy

Charge

Velocity

Solution

Question 7

$$\omega\propto n^3$$

$$\omega\propto\dfrac{1}{ n^3}$$

$$\omega\propto n^2$$

$$\omega\propto\dfrac{1}{ n^2}$$

Solution

Question 8

$$v\propto { V }^{ 2 }$$

$$v\propto \sqrt { V } $$

$$v\propto \cfrac { 1 }{ V } $$

$$v\propto V$$

Solution

Question 9

$${ n }_{ 1 }=1,{ n }_{ 2 }=2,3,4,\dots $$

$${ n }_{ 1 }=2,{ n }_{ 2 }=3,4,5,\dots $$

$${ n }_{ 1 }=3,{ n }_{ 2 }=4,5,6,\dots $$

$${ n }_{ 1 }=4,{ n }_{ 2 }=5,6,7,\dots $$

Solution

Question 10

line emission spectrum

band emission spectrum

continuous emission spectrum

line absorption spectrum

Solution

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