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Structure Of Atom

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Question
CBSEENCH11008373
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A 0.66 kg ball is moving with a speed of 100 m/s. The associated wavelength will be
(h = 6.6 x 10-34 Js)

  • 6.6 x 10-32 m

  • 6.6 x 10-34 m

  • 1 x 10-35 m

  • 1 x 10-32

Solution

C.

1 x 10-35 m

straight lambda space equals space straight h over mv space equals space fraction numerator 6.6 space straight x space 10 to the power of negative 34 end exponent over denominator 0.66 space straight x space 100 end fraction space equals space 10 to the power of negative 35 end exponent

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Question
CBSEENCH11008338
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According to the Bohr theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?

  • n= 6 to n = 1

  • n = 5 to n = 4

  • n= 6 to n = 5 

  • n = 5 to n = 3 

Solution

C.

n= 6 to n = 5 

increment straight E space proportional to open square brackets space fraction numerator 1 over denominator straight n subscript 1 superscript 2 end fraction minus fraction numerator 1 over denominator straight n subscript 2 superscript 2 end fraction close square brackets space comma space where space straight n subscript 2 greater than straight n subscript 1
Energy of photon obtained from the transition n = 6 to n = 5 will have least energy.

Question
CBSEENCH11008255
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Based on equation
E=-2.178 x 10-18 J open parentheses straight Z squared over straight n squared close parentheses certain conclusions are written. Which of them is not correct?

  • The negative sign in the equation simply means that the energy of an electron bound to the nucleus is lower than if would be if the electrons were at the infinite distance from the nucleus.

  • Larger the value of n, the larger is the orbit radius

  • Equation can be used to calculate the change in energy when the electron changes orbit

  • For n=1 the electron has a more negative energy than it does for n=6 which means that the electron is more loosely bound in the smallest allowed orbit.

Solution

D.

For n=1 the electron has a more negative energy than it does for n=6 which means that the electron is more loosely bound in the smallest allowed orbit.

If n=1,
E1 = - 2.178 x 10-18 Z2 J
If n=6
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From the above calculation, it is obvious that electron has a more negative energy than it does for n=6. it means that electron is more strongly bound in the smallest allowed orbit.

Question
CBSEENCH12011010
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Calculate the energy in joule corresponding to light of wavelength 45mm: (Planck's constant h=6.63 x10-34)Js; speed of light c= 3 x 108 ms-1)

  • 6.67 x 1015

  • 6.67 x 1011

  • 4.42 x 10-15

  • 4.42 x 10-18

Solution

D.

4.42 x 10-18

The wavelength of light is related to its energy by the equation,
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Question
CBSEENCH11008438
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Given: The mass of electron is 9.11 x 10-31 kg
Planck constant is 6.626 x 10-34 Js,
the uncertainty involved in the measurement of velocity within a distance of 0.1 A is:

  • 5.79 x 106 ms-1

  • 5.79 x 107 ms-1

  • 5.79 x 108 ms-1

  • 5.79 x 105 ms-1

Solution

A.

5.79 x 106 ms-1

By Heisenberg's uncertainty principle
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