A photon will have less energy, if its

Important Questions on Dual Nature of Matter and Radiation

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

If a semiconductor photo diode can detect a photon with a maximum wavelength of $400 \mathrm{nm}$, then its band gap energy is: Planck's constant $h=6.63\times {10}^{-34} \mathrm{J} \mathrm{s}$ 
Speed of light $c=3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$.

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

Two particles move at right angle to each other. Their de Broglie wavelengths are ${\lambda }_1$ and ${\lambda }_2$ respectively. The particles suffer perfectly inelastic collision. The de Broglie wavelength $\lambda$ of the final particle, is given by:

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A $2\mathrm{ }\mathrm{m}\mathrm{W}$ laser operates at a wavelength of $500\mathrm{ }\mathrm{n}\mathrm{m}$ . The number of photons that will be emitted per second is:
[Given Planck's constant $\mathrm{h}=6.6\times {10}^{-34}\mathrm{ }\mathrm{J}\mathrm{ }\mathrm{s},$ speed of light $\mathrm{c}=3.0\times {10}^8\mathrm{ }\mathrm{m}/\mathrm{s}$ ]

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A photodiode sensor is used to measure the output of a $300 \mathrm{W}$ lamp kept $10 \mathrm{m}$ away The sensor has an opening of $2 \mathrm{cm}$ in diameter. How many photons enter the sensor if the wavelength of the light is $660 \mathrm{nm}$ and the exposure time is $100 \mathrm{m} \mathrm{s}$. (Assume that all the energy of the lamp is given off as light and $\mathrm{h}=6.6\times {10}^{-34} \mathrm{J} \mathrm{s}$ )

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A pulse of light of duration $100 \mathrm{ns}$ is absorbed completely by a small object initially at rest. Power of the pulse is $30 \mathrm{mW}$ and the speed of light is $3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$. The final momentum of the object is

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A light beam of intensity $20 \mathrm{W} {\mathrm{cm}}^{-2}$ is incident normally on a perfectly reflecting surface of sides $25 \mathrm{cm}\times 15 \mathrm{cm}$. The momentum imparted to the surface by the light per second is

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

Light is incident normally on a completely absorbing surface with an energy flux of $25\mathrm{ }\mathrm{W}\mathrm{ }\mathrm{c}{\mathrm{m}}^{-2}$ . If the surface has an area of $25\mathrm{ }\mathrm{c}{\mathrm{m}}^2$ , the momentum transferred to the surface in $\text{40}\text{min}$ time duration will be:

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

The wavelength of $1 \mathrm{keV}$ photon is $1.24\times {10}^{-9} \mathrm{m}.$ What is the frequency of $1 \mathrm{MeV}$ photon?

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A $160 \mathrm{W}$ light source is radiating light of wavelength $6200 \stackrel{°}{\mathrm{A}}$ uniformly in all directions. The photon flux at a distance of $1.8 \mathrm{m}$ is of the order of (Planck's constant$=\left.6.63\times {10}^{-34} \mathrm{J} \mathrm{s}\right)$,

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A $160 \mathrm{W}$ infrared source is radiating light of wave length $50000 \stackrel{°}{\mathrm{A}}$ uniformly in all directions. The photon flux at a distance of $1.8 \mathrm{m}$ is the order of

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

To excite the spectral line of wavelength $4960 \stackrel{\circ }{\mathrm{A}}$ of an atom, an excitation energy of $7.7 \mathrm{eV}$ is required. The ground state energy of the atom is $10.5 \mathrm{eV}$. The energies of two levels involved in the emission of $4960 \stackrel{\circ }{\mathrm{A}}$ line are (Assume, $hc=1240 \mathrm{eV} \mathrm{nm}$, where $h$ is Planck's constant and $\mathrm{c}$ is speed of light)

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

An electron and a photon have the same wavelength of ${10}^{-9} \mathrm{m}.$ If E is the energy of the photon and p is the momentum of the electron, the magnitude of $\frac{E}{p}$ in S.I. units is,

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A monochromatic source of radiation is operating at $100 \mathrm{W}$ power. The source emits $2\times {10}^{20}$ photons per second. The wavelength of light will be $\left(h=6.67\times {10}^{-34} \mathrm{J} \mathrm{s}\right)$

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

Two sources of light emit X-rays of wavelength $1 \mathrm{nm}$ and visible light of wavelength $500 \mathrm{nm}$, respectively. Both the sources emit light of the same power $200 \mathrm{W}$. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is:

EASY

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A potassium chloride crystal has an energy band gap of $6 \mathrm{eV}$. What wavelength of light for which the crystal is completely transparent? (Assume $hc=1242 \mathrm{eV} \mathrm{mm}$)

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

The momentum of a photon is $2.5\times {10}^{-29} \mathrm{kg} \mathrm{m} {\mathrm{s}}^{-1}$. Its frequency will be

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

The number of photons falling per second on a completely darkened plate to produce a force of $6.62\times {10}^{-5} N$ is $n$. If the wavelength of the light falling is $5\times {10}^{-7} \mathrm{m},$ then $n=\dots \times {10}^{22}.\left(h=6.62\times {10}^{-34}\mathrm{ J}-\mathrm{s}\right)$

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A $1.5 \mathrm{kW}$ (kilo-watt) laser beam of wavelength $6400 \stackrel{\circ }{\mathrm{A}}$ is used to levitate a thin aluminium disk of same area as the cross-section of the beam. The laser light is reflected by the aluminium disk without any absorption. The mass of the foil is close to,

MEDIUM

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths $r=\frac{{\lambda }_1}{{\lambda }_2}$, is given by:

HARD

Physics>Modern Physics>Dual Nature of Matter and Radiation>Photon Theory of Light

A photon of wavelength $\lambda$ is absorbed by an electron confined to a box of length $\sqrt{\frac{35h\lambda }{8mc}}$, As a result, the electron makes a transition from state, $k=1$ to the state, $n.$ Subsequently, the electron transits from the state $n$ to the state $m$ by emitting a photon of wavelength ${\lambda }^{\prime }=1.85\lambda .$ Then