Question 52. 24. What will be the new wavelength when the accelerating potential is increase to 4V? (a) The minimum amount of energy required to take out an electron from the surface of metal. 1.The following table gives the values of work functions for a few sensitive metals. On the other hand, the photoelectric effect is supported by the particle nature of light. (b) (i) Saturation current depends only on the intensity of incident radiation but is independent of the frequency of incident radiation. De Broglie wavelength of the bullet is given by the relation: De Broglie wavelength of the ball is given by the relation: De Broglie wavelength of the dust particle is given by the relation: 8. It is clear from eq. In the relativistic domain, mass is given as: Hence, the radius of the circular path is given as: 14.An electron gun with its collector at a potential of 100 V fires out electrons in a spherical bulb containing hydrogen gas at low pressure of Hg). Velocity of photoelectrons increases with the decrease in the wavelength of the incident light. When an electron is accelerated through a potential difference V then the energy acquired by electron, When these high energy electrons fall on target T of high atomic number, then X-rays are produced, whose wavelength is given by, The shortest wavelength of X-rays emitted is. Nuclei ( All ) Select Topic. Thus slope is equal to the ratio of planck’s constant to the charge on electron. The force exerted on the electron is given as: θ = Angle between the magnetic field and the beam velocity. Then by free body diagram (fig. Dual Nature of Radiation and Matter ( All ) Select Topic. for an emitted electron, applying law of conservation of energy. (b) a neutron, would have the same de Broglie wavelength. This is the Einstein’s photoelectric equation. Ammeter to measure the value of photoelectric current. Photoelectric emission takes place when a light of frequency 6×1014 Hz is incident on the metal surface. They have higher penetrating power. ), the electron may escape from the surface. Mathematically, if   p = fixed  , Then, Δp→0, Δx→∞. (a) Quarks inside protons and neutrons are thought to carry fractional charges [(+2/3)e; ( – 1/3)e]. Ans. This does not affect the energy of the radiation. What is the threshold frequency for photoemission of electrons? On further increasing the positive potential, photoelectric current reaches a maximum value, beyond which it remains fixed even when positive potential is increased. The work function for the metal is given to be about 2 eV. 3. of emitted electrons be greater? Physicswallah Typed Notes. 23.Crystal diffraction experiments can be performed using X-rays, or electrons accelerated through appropriate voltage. The energy (E1) of a radio photon is very less, but the number of photons (n) emitted per second in a radio wave is very large. Considering the above equation, 2 cases are possible: It means that the wavelength has a fixed value and the wave is extended infinitely throughout the wave. The first type of scattered wave has same wavelength (λ, ) as the incoming X-rays, while second type has a longer wavelength (λ) than incident rays (First type of X-rays are called unmodified x-rays, while second type of X-rays are called modified X-rays.) Assume that the frequency of the radiation incident on a metal plate is greater than its threshold frequency. The energy E of a photon is equal to a constant h times its frequency ν, When a photon arrives at surface, it is absorbed by an electron. 2.Mention one physical process for the release of electron from the surface of a metal? They are not deflected by electric or magnetic field. On the other hand, saturation current got higher for higher values of intensity of absorbed light, The variation of photoelectric current was plotted against the potential for 3 different values of frequency of incident light (keeping the intensity constant). 27. 4. Another vacancy is now created in the ‘L’ shell which is again filled up by another electron jump from one of the upper shell (M) which results in the emission of another photon, but of different X-rays frequency. Question 1. According to which, when a monochromatic beam of X-rays (wavelength λ, ) strikes the electron in a carbon target, two types of X-rays are scattered. It is clear from next topic that Compton effect confirm the validity of p = h/λ for photons, and the photoelectric effect confirms the validity and E = hν for photons. Ans.The wavelength of a wave associated with a moving football is extremely small, which cannot be detected. If an electron beam of energy eV (electron volts) is incident on the target material; the electrons are suddenly stopped. Hence, Mo and Ni will not show photoelectric emission. Dual Nature of Radiation. The quark structure of protons and neutrons appears at the minute length-scale of 10-15m or less. Kinetic energy (K) and velocity (v) are related as: De Broglie wavelength  and velocity (v) are related as: Using equation (2) in equation (1), we get: Hence, the kinetic energy of the neutron is J or eV. In the above formula, the expression for energy can only be used in the non-relativistic limit, i.e., for v << c. When very high speeds are concerned, the relativistic domain comes into consideration. Interference, diffraction etc. (a) we consider a single drop of mass m carrying a negative charge –q in the absence of electric field. A. MIlikan, in 1913 performed experiments to calculate the charge on an oil drop (popularly known as Milikan’s oil drop experiment), He observed that, every time the charge came to be an integral(whole number) multiple of a small charge (), which is actually the charge on an electron, MIlikan concluded that charge on a matter is quantized (discrete), The process of emission of electrons from the metal surface when a certain amount of energy is absorbed by the metal, is called electron emission, There are free electrons on the metal surface, present in the outermost (valence) shell that are loosely bound to the nucleus, These electrons are emitted when a certain minimum amount of external energy is provided to the metal surface. Justify your answer in each case? Dual nature of radiation: Wave theory of electromagnetic radiation explains the phenomenon of interference, diffraction, and polarisation. Ans.Kinetic energy of the electron, Ek= 120 eV. 18.Ultraviolet light of wavelength 2271 ¦ from a 100 W mercury source irradiates a photo-cell made of molybdenum metal. It is difficult to remove a free electron from copper than from sodium? If not, in what way is it modified? 6.The wavelength  of a photon and debroglie wavelength of an electron have the same value. Ans. 207, Laxmideep Building Plot No. What is the de Broglie wavelength of a nitrogen molecule in air at 300 K? Compton treated this processes as a collision between a photon & an electron. Ans.Mo and Ni will not show photoelectric emission in both cases. Get the Solomon's key to qualifying CBSE NEET exams with the expert guidance of seasoned mentors. Ans.An X-ray probe has a greater energy than an electron probe for the same wavelength. Hence, we assume the dual nature of light. The luminous streaks travelling from cathode to anode, below the pressure 0.01 mm. 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