The number of protons, neutrons and electrons in 17571Lu respectively, are:
1. 104, 71 and 71
2. 71, 71 and 104
3. 175, 104 and 71
4. 71, 104 and 71
Which of the following conclusions could not be derived from Rutherford's α-particle scattering experiment?
1. | Most of the space in the atom is empty. |
2. | The radius of the atom is about 10-10 m while that of a nucleus is 10–15 m. |
3. | Electrons move in circular path of fixed energy called orbits. |
4. | Electrons and the nucleus are held together by electrostatic forces of attraction. |
The number of electrons, protons and neutrons in a species are equal to 18, 16 and 16 respectively. The proper symbol of the species is :
1. | 3216S2− | 2. | 3218S2− |
3. | 168S | 4. | 3216S |
Which of the following statement is not correct about the characteristics of cathode rays?
1. | They start from the cathode and move towards the anode |
2. | They travel in straight line in the absence of an external electrical or magnetic field |
3. | Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray tube |
4. | Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube |
A monochromatic infrared range finder of power 1milli watt emits photons with wavelength 1000 nm in 0.1 second. The number of photons emitted in 0.1 second is:
(Given: h = 6.626×10−34J s , c = 3×108m s−1, Avogadro number = 6.022×1023)
1. 30×1037
2. 5×1014
3. 30×1034
4. 5×1011
Match types of wave in Column-I with the corresponding frequency in Column-II and mark the appropriate option:
Column-I
(Types of Wave)
|
Column-II (Corresponding Frequency) |
||
A. | X-rays | I. | v=100−104 Hz |
B. | Ultraviolet wave (UV) | II. | v=1010 Hz |
C. | Long radio waves | III. | v=1016 Hz |
D. | Microwave | IV. | v=1018 Hz |
A | B | C | D | |
1. | IV | I | III | II |
2. | I | IV | II | III |
3. | I | IV | III | II |
4. | IV | III | I | II |
Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. The work function (W0) of the metal is:
1. 3.109 × 10–20 J
2. 2.922 × 10–19 J
3. 4.031 × 1019 J
4. 2.319 × 10–18 J
When electromagnetic radiation of wavelength 300 nm falls on the surface of sodium, electrons are emitted with a kinetic energy of 1.68 ×105 J mol–1. The minimum energy needed to remove an electron from sodium and the maximum wavelength that will cause a photoelectron to be emitted are, respectively:
1. 2.31 × 105 J mol–1, 517 nm
2. 23.1 × 105 J mol–1, 517 nm
3. 3.31 × 105 J mol–1, 417 nm
4. 33.1 × 105 J mol–1, 417 nm
The energies E1 and E2 of two radiations are 25 eV and 50 eV respectively. The relation between their wavelengths i.e., λ1 and λ2 will be:
1. λ1=2λ2
2. λ1=4λ2
3. λ1=12λ2
4. λ1=λ2