1900's Physics and Wave

Q.

The total energy of an electron in the n^th orbit of a hydrogen atom is given by the formula E_n = -13.6 eV/n². What does the negative energy for an electron indicate?

1. Electrons have both wave and particle-like properties.

2. The electron has a negative charge.

3. The electron is far away from nucleus.

4. Energy of electron in an atom is lower than the energy of an electron far away from nucleus.

Q. The total number of electrons in 4.2g of N3- ion is:

Q.

What are the uses of X-rays?

Q. 46.Energy of electron of He^+ ion in the 3rd orbit is (IE of H atom is 13.6eV)

Q.

The de Broglie wavelength associated with a ball of mass. $200g$ and moving and moving at a speed of $5metres/hour$, is in the order of ($h$ = $6.625\times {10}^{-34}Js$)

1. 1.342 x 10^-15 m

2. 1.463 x 10^-20 m

3. 2.014 x 10^-25 m

4. 2.385 x 10^-30 m

Q. the de broglie wavelength for helium atom at room temp is

Q.

What is the frequency of a photon that has an energy of 3.7 x 10^-18J?

1. 1.8 x 10^-16

2. 5.6 x 10¹⁵

3. 0.55 X 10⁺¹⁶

4. 2.5 x 10^-15

Q. Wavelength of the de-Broglie wave of an electron revolving in the fourth orbit of the hydrogen atom is (r0 is the Bohrs radius) Options: a- 25 r0 b- r0 c-10 r0 d- 8 r0

Q.

When a certain metal was irradiated with light of frequency $1.6\times {10}^{16}Hz$, the photoelectrons emitted had twice the kinetic energy as the photoelectrons emitted when the same metal was irradiated with light of frequency $1.0\times {10}^{16}Hz$. Calculate the threshold frequency ($v_0$) for the metal.

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Q.

What is the energy of a photon that has a wavelength of 12.3 nm?

1. 1.51 × 10^-17 J

2. 4.42 × 10^-23 J

3. 1.6 x 10^-17J

4. 1.99 × 10^-25 J

Q. 3.Calculate the number of waves made by a Bohr electron in one complete revolution in nth orbit of H atom.If the ratio of de-Broglie wavelength associated with electron moving in nth orbit and 2nd orbit is 1.5

Q.

It takes 495.8 kJ/mol of energy to ionize sodium. What frequency (s^-1) and wavelength (nm) of light would be required to ionize sodium?

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Q. Who invented Chemistry?

Q. 19. Why the e/m ratio of proton changes from each gas while the e/m ratio of the electron remains same and why the hydrogen atom doesnt have the neutron

Q. 26. Calculate energy required to excite electron from ground state to 5th orbit of H atom

Q.

Life period of nascent hydrogen?

Q. The total number of electron in 2.0g of D2O to that in 1.8 g of H2

Q. 58. Explain the relationship between intensity and frequency? Is inversely or directly proportional and how?

Q. Colours in thin films are because of:

1. Polarisation
2. Interference
3. Reflection
4. Diffraction

Q.

How much energy is needed to ionize a hydrogen atom if electron is present in n=1 orbit?

1. 3.4eV

2. 13.6 eV

3. 1 eV

4. 10.2 eV

Q. A beam of helium atoms moves with a velocity of 2*10^4 m/s.Find the wavelength of particles constituting with the beam.How will mass of helium atom be calculated?

Q. 86. The increasing order for the values of e/m for electron , proton , neutron and alpha particle?

Q. 33.Calculate first excitation energy of electron in hydrogen atom.

Q. A $20$ watt bulb emits monochromatic light of wavelength $500$ nm. The number of photons emitted per second by the bulb is

Q. If $E_1,E_{2}and{E}_3$ represent respectively the kinetic energies of an electron, an alpha particle and a proton, each having same de-Broglie wavelength then?

1. E₁>E₃>E₂

2. E₂>E₃>E₁

3. E₁>E₂>E₃

4. E₁=E₂=E₃

Q. Velocity of the electron emitted by Li(Φ (work function) = 2.90 eV) of light of frequency 4.77x10¹5 S-1 is absorbed is (1 eV = 1.6 × 10-¹⁹)
(a) 3.10 x 106 ms-¹
(b) 6.20 x 108 ms-¹
(c) 2.51×106 ms -¹
(d) 4.86x108 ms -1

Q.

The work function of a metal is 4.2 $e\nu$. If radiations of $2000\stackrel{o}{A}$ fallon the metal, then the kinetic energy of the fastest photoelectron is

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Q. in which of the following reaction boron does not as reducing agent ? (1) B+CO2--> (2) B+ Mg--> (3) B+ SiO2 --> (4) B+ HNO3--

Q. 2 Calculate the threshold frequency of metal from which the photoelectrons are emmited with zero velocity when exposed to radiation of wavelength 6800A.

Q. 65. the value of plancks constant is 6.63\ast10^{-34} Js. the speed of light is 3\ast10^{17}nms^{-1} . which value is closest to the wavelength in nm of a quantum of light with frequency of 6\ast10^{15}s^{-1}?