Advertisements
Advertisements
प्रश्न
Photons absorbed in matter are converted to heat. A source emitting n photon/sec of frequency ν is used to convert 1 kg of ice at 0°C to water at 0°C. Then, the time T taken for the conversion ______.
- decreases with increasing n, with ν fixed.
- decreases with n fixed, ν increasing.
- remains constant with n and ν changing such that n ν = constant.
- increases when the product n ν increases.
विकल्प
b and d
a, c and d
a and d
a, b and c
उत्तर
a, b and c
Explanation:
We know that energy spent to convert ice into water
`E_("absorb")` = mass × latent heat
∴ E = mL = (1000 g) × (80 cal/g)
E = 80000 cal
Energy of photons used = nT × E = nT × hv ....[∵ E = hv]
So, nThv = mL ⇒ T = `(mL)/(nhv)`
∴ `T oo 1/n`, when v is constant.
Thus, time taken for conversion decreases with increasing n with v kept constant.
`T oo 1/v`, when n remains constant.
Thus, time taken for conversion decreases with increasing v with n kept constant.
⇒ `T oo 1/(nv)`
Thus, time taken for conversion decreases with increase in product of nv and T is constant, if nv is constant.
APPEARS IN
संबंधित प्रश्न
The energy flux of sunlight reaching the surface of the earth is 1.388 × 103 W/m2. How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of 550 nm.
A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm.
(a) What is the energy per photon associated with the sodium light?
(b) At what rate are the photons delivered to the sphere?
(a) An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at 0.45 Å. What is the maximum energy of a photon in the radiation?
(b) From your answer to (a), guess what order of accelerating voltage (for electrons) is required in such a tube?
Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about photons! The second number tells you why our eye can never ‘count photons’, even in barely detectable light.
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 (∼10−10 W m−2). Take the area of the pupil to be about 0.4 cm2, and the average frequency of white light to be about 6 × 1014 Hz.
When an electron strikes the target in a Coolidge tube, its entire kinetic energy
(a) is converted into a photon
(b) may be converted into a photon
(c) is converted into heat
(d) may be converted into heat.
In interaction of radiation with matter, radiation behaves as if it is made up of particles called ______.
If E and p are the energy and the momentum of a photon respectively, then on reducing the wavelength of photon
A source of monochromatic light liberates 9 × 1020 photon per second with wavelength 600 nm when operated at 400 W. The number of photons emitted per second with wavelength of 800 nm by the source of monochromatic light operating at same power will be:
The energy of a photon of wavelength 663 nm is ______.
The energy of a photon of wavelength λ is ______.
