Recent questions tagged medium

A neutron beam of energy E scatters from atoms on a surface with a spacing $d= 0.1 nm$ . The first maximum of initially in the reflected beam occurs at $ \theta= 30^{\circ}$ . What is the kinetic energy E of the beam in eV?

asked Jul 4, 2016 by meena.p

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There are two sources of light each emitting with a power of 100 w. one emits X- rays of wave length 1 nm and the other visible light at 500 nm. Find the radio of no of photons of x- rays to the photons of visible light of the given wave length ?

asked Jul 4, 2016 by meena.p

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In the explanation of photo electric effect , we assume one photon of frequency $\alpha$ collide with an electron and transfer its energy . This leads to the equation for the maximum energy $E_{max}$ of the emitted electron as $ E_{max}= h \alpha - \phi _0$ where $ \phi _0$ is the work function of the metal. If an electron absorbs 2 photons (each of frequency ) what will be the maximum energy for the emitted electron ?

asked Jul 4, 2016 by meena.p

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A proton and an $\alpha $ particle are accelerated , using the same potential difference . How are the de- Broglie wave length $ \lambda_p$ and $\lambda_{\alpha}$ related to each other ?

asked Jul 4, 2016 by meena.p

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Photons absorbed in matter are converted to heat , A source emitting n photons/ sec of frequency $\gamma$ is used to convert $1 kg$ of ice at $ 0^{\circ}C$ to water at $ 0^{\circ}C$ . Then , the time taken for the conversion .

asked Jul 4, 2016 by meena.p

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Two particles $A_1$ and $A_2$ of masses $m_1$ and $m_2 (m_1 > m_2)$ have the same de -broglie wave length then

asked Jul 4, 2016 by meena.p

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Relativistic correction become necessary when the expression for the kinetic energy $\large\frac{1}{2}$$mv^2$ becomes comparable with $mc^2$ where m is the mass of the particle . At what de- broglie wave length will relativistic correction become important for an electron ?

asked Jul 4, 2016 by meena.p

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An electron (mass m) with an initial velocity $ \overrightarrow{v} =v_0 \hat i$ is in an electric field $ \overrightarrow{E} = E_0 \hat j$. If $\lambda_0 = \large\frac{h}{mv_0}$ , Its de-Broglie wave length at time t is given by

asked Jul 4, 2016 by meena.p

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An electron (mass m) with an initial velocity $ \overrightarrow{v} =v_0 \hat i (v_0 > 0) $ is in an electric field $ \overrightarrow{E} =- E_0 \hat i (E_0= constant >0) $ . Its de-Broglie wave length at time t is given by

asked Jul 4, 2016 by meena.p

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The wave length of a photon needed to remove a proton from a nucleus which is bound to the nucleas with 1 Mev energy is nearly

asked Jun 30, 2016 by meena.p

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The energy and momentum of an electron are related to the frequency and wave length of the associated matter wave by the relation $E= h \gamma,P=\large\frac{h}{\lambda}$ But while the value of $\lambda $ is physically significant the value of $\gamma$ (and therefore the value of phone speed ) has no physical significance why ?

asked Jun 30, 2016 by meena.p

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Every metal has a definite work function. Why do all photo electrons not come out with the same energy if incident radiation is monochromatic ? why there an energy distribution of photo electron ?

asked Jun 30, 2016 by meena.p

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Why should gases be insulators at ordinary pressures, and start conducting at low pressures.

asked Jun 30, 2016 by meena.p

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What is so special about the combination e/m ? Why do we not simply talk of e and m separately ?

asked Jun 29, 2016 by meena.p

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Crystal diffraction experiment can be performed using x- rays or electron acceleration through appropriate voltage ? Which probe has grater energy ? An x -ray photon or the electron ?

asked Jun 28, 2016 by meena.p

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Light of intensity $10^{-5} \;wm^{-2} $ falls on a sodium photocell of surface area $2 cm^2$ Assuming that the top 5 layers of sodium absorb the incident energy, estimate the time required for photo electric emission in the wave picture of radiation . The work function of the metal is given to be about 2 ev . What is the implication of your answer ? Effective atomic area $=10^{-20} m^2$

asked Jun 28, 2016 by meena.p

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A mercury lamp is a convenient source for studying frequency dependence of photo electric emission , Since it gives a number of spectral lines rating from the uv to the red end of the visible spectrum . In our experiment with rubidium photo- cell , the following lines from a mercury source where used . $ \lambda_1 = 3650 A^{\circ}, \lambda_2 = 4047 A^{\circ}, \lambda_1 = 4358 A^{\circ}, \lambda_4 = 5461 A^{\circ}, \lambda_5 = 6907 A^{\circ}$The stopping voltages respectively were measured to be : $V_{o1}= 1.28 \;v , V_{o2}= 0.95 \;v, V_{o3}= 0.74 \;v, V_{o4}= 0.16\;v, V_{o5}= 1.28 \;v$ Estimate the threshold frequency and work function for the material .

asked Jun 27, 2016 by meena.p

1 answer

A mercury lamp is a convenient source for studying frequency dependence of photo electric emission , Since it gives a number of spectral lines rating from the uv to the red end of the visible spectrum . In our experiment with rubidium photo- cell , the following lines from a mercury source where used . $ \lambda_1 = 3650 A^{\circ}, \lambda_2 = 4047 A^{\circ}, \lambda_1 = 4358 A^{\circ}, \lambda_4 = 5461 A^{\circ}, \lambda_5 = 6907 A^{\circ}$The stopping voltages respectively were measured to be : $V_{o1}= 1.28 \;v , V_{o2}= 0.95 \;v, V_{o3}= 0.74 \;v, V_{o4}= 0.16\;v, V_{o5}= 1.28 \;v$ Determine the value of plark's constant be

asked Jun 27, 2016 by meena.p

1 answer

Monochromatic radiation of wave length $640.2 nm$ from a neon lamp irradiates a photo sensitive material made of calcium or tungsten. The stopping voltage is mentioned to be $0.54\;v$ . The source is replaced by an iron source and its $427.2\;nm$ line irradiates the same photo cell . predict the new stopping voltage .

asked Jun 27, 2016 by meena.p

1 answer

ultra violet light of wave length $2271A^{\circ}$ from a 100 w mercury source irradiates a photocell made of molybdenum metal. If the stopping potential is $13.v$ estimate the work function of the metal. How would the photo cell respond to a high intensity $(10^5wm^{-2})$ red light of wave length $6328\;A^{\circ}$ produced by $He- Ne$ laser ?

asked Jun 27, 2016 by meena.p

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The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive . Take the area of the pupil to be about $0.4\;cm^2$ and the average frequency of white light to be found $6 \times 10^4 Hz$

asked Jun 27, 2016 by meena.p

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Estimate the number of photons emitted per second by a Mw transmitter of 10 Kw power emitting radio waves of length 500 m

asked Jun 27, 2016 by meena.p

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An x-ray tube produces a continuous spectrum of radiation with its short wave length end at $0.45 A^{\circ}$ what is the maximum energy of a photon in the radiation ?

asked Jun 27, 2016 by meena.p

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An electron gun with its anode at a potential $100\;v$ fires out electrons in a spherical bulls containing hydrogen gas at low pressure $(10^{-2}\;mm\;of\;Hg)$ . A magnetic field of $2.83 \times 10^{-4}\;T$ curves the path of the electron in a circular orbit of radius 12.0 cm (The path can be viewed because the gas ions in the path focus the beam by attracting electrons and emitting light by electron capture. this method is known as "fine beam tube " method. Determine e/m from the data .

asked Jun 24, 2016 by meena.p

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A mono energetic electron beam with electron speed of $5.20 \times 10^6 ms^{-1}$ is subjected to a mognetic field of $1.30 \times 10^{-4}\;T$ , normal to the beam velocity .What is the radius of the circle traced by the beam , given $\large\frac{e}{m}$ for electron equals $1.76 \times 10^{11} ckg^{-1}$Is the formula you employ valid for calculating radius of the path of 20 Mev electron beam ? If not in what way is it modified ?

asked Jun 24, 2016 by meena.p

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A mono energetic electron beam with electron speed of $5.20 \times 10^6 ms^{-1}$ is subjected to a mognetic field of $1.30 \times 10^{-4}\;T$ , normal to the beam velocity .What is the radius of the circle traced by the beam , given $\large\frac{e}{m}$ for electron equals $1.76 \times 10^{11} ckg^{-1}$

asked Jun 24, 2016 by meena.p

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What is the de-Broglie wavelength of a nitrogen molecule in air at $300\;K$ Assume that the molecule that the molecule is moving with the root- means - square speed of molecules at this temperature ? (Atomic mass of nitrogen = $14.0076\;u$) given : $h= 6.63 \times 10^{-34}\;Js,m_n= 1.675 \times 10^{-27}\;kg; k= 1.8 \times 10^{-23}JK^{-1}$

asked Jun 24, 2016 by meena.p

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Show that the wave length of electro magnetic radiation is equal to the de-Broglie wave length of its quantum (photon)

asked Jun 23, 2016 by meena.p

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What is the de-Broglie wave length of a bullet of mass $0.040\;kg$ travelling at the speed of $1.0kms^{-1}$? $h= 6.63 \times 10^{-34}\;Js$

asked Jun 23, 2016 by meena.p

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The work function for a certain metal is $4.2\;ev$ will this metal give photo electric emission for incident radiation of wave length $330 nm? $

asked Jun 22, 2016 by meena.p

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Two slits are 1 mm apart and the screen is placed 1 m away. What is the fringe separation when blue green light of wave length 500 nm is used ?

asked Jun 20, 2016 by meena.p

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Find the minimum thickness of a film which will strongly reflected the light of wavelength $589\;nm$ The refractive index of the material of the film is $1.25$

asked Jun 20, 2016 by meena.p

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The diameter of the pupil of human eye is about $2mm$. Human eye is the most sensitive to the wave length $555\;nm$ Find the limit of resolution of human eye.

asked Jun 20, 2016 by meena.p

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Unpolarized light incident on a plane glass surface. What should be the angle of incidence so that the reflected and refracted and refracted ray are perpendicular to each other ? $(\mu =1.5)$

asked Jun 20, 2016 by meena.p

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A beam of light consisting of wave length 650 nm and 520 nm, is used to obtain interference finger in a Young's double slit experiment . Find the distance of the third bright fringe on the screen from the central maximum for wave length 650 nm

asked Jun 20, 2016 by meena.p

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Yellow light is used in a single slit diffraction experiment is used in a single slit diffraction experiment with slit width $0.6\;mm$ . If yellow light is replaced by x- rays, then the observed pattern will reveal

asked Jun 20, 2016 by meena.p

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Diameter of human eyelens is 2 mm. What will be the minimum distance between two points to resolve , which is situated at a distance of 50 m from eye ? The wavelength of light is $5000 A^{\circ}$

asked Jun 20, 2016 by meena.p

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The angular resolution of a $10\; cm$ diameter telescope at a wavelength of $5000 A^{\circ}$ is of the order of

asked Jun 20, 2016 by meena.p

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Two coherent light beams of intercity I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are :

asked Jun 20, 2016 by meena.p

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How does the angular separation between fringes in single- slit diffraction experiment change when the distance of separation between the slit and screen is doubled ?

asked Jun 17, 2016 by meena.p

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A star is moving away from an observer with a speed of $500 kms^{-1}$. Calculate the Doppter shift if the wavelength of light emitted by the star is $6000 A^{\circ}$

asked Jun 17, 2016 by meena.p

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If the two slits in young's experiment have width $1:4$ deduce the ratio of intensity at maxima and minima in the interference pattern .

asked Jun 17, 2016 by meena.p

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Why is the diffraction of sound waves more evident in daily experience than that of light wave ?

asked Jun 16, 2016 by meena.p

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Consider sunlight incident on a pinhole of width $10^3\;A$ . The image of the pinhole seen on a screen shall be

asked Jun 16, 2016 by meena.p

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Consider a light beam incident from air to a glass slab at Brewster's angle as shown. A Polaroid is placed of the emergent ray at a point P and rotated about an axis passing through the center and perpendicular to the plane of the polaroid .

asked Jun 15, 2016 by meena.p

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The direction of ray of light incident on a concave mirror is shown by PQ, while direction in which the ray would travel after reflection shown in this figure. marked 1,2,3 and 4. Which of the four rays shows the direction of reflected ray ?

asked Jun 15, 2016 by meena.p

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The phenomenon involved in the reflection of radio waves by ionosphere is similar to

asked Jun 15, 2016 by meena.p

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The radius of curvature of a plano - convex . lens is 20 cm If the refractive index of the material of the lens be $1.5$ it will

asked Jun 15, 2016 by meena.p

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You are given four sources of light each one providing a light of a single colour - red, blue , green and yellow . Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incident at an interface of two media is $90^{\circ}$ which of the following : Statement is correct if the source of yellow light is replaced with that of other lights without changing the angle incident ?

asked Jun 15, 2016 by meena.p

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An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus at the focus . The image

asked Jun 15, 2016 by meena.p

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