Description : A hydrogen like gas emits radiation of wavelengths `460 Å, 828 Å` and `1035Å`, only. Assume thar the atoms have only two excited states and the differ
Last Answer : A hydrogen like gas emits radiation of wavelengths `460 Å, 828 Å` and `1035Å`, only. Assume ... of the ground state and the first excited state.
Description : Maximum amount of thermal radiation is emitted at all wavelengths at any specified temperature by a/an __________ body. (A) Grey (B) Black (C) Opaque
Last Answer : (A) Grey
Description : A dye absorbs a photon of wavelength `lambda` and re`-` emits the same energy into two phorons of wavelengths `lambda_(1)` and `lambda_(2)` respective
Last Answer : A dye absorbs a photon of wavelength `lambda` and re`-` emits the same energy into two phorons of wavelengths ` ... 2))/((lambda_(1)+lambda_(2))^(2))`
Description : Sodium fluorescein: a. has a higher affinity for plasma protein than indocyanine green. b. does not leak from the choroidal vasculature. c. does not leak from normal retinal vasculature. d. emits light of longer wavelengths than the one it absorbs
Last Answer : does not leak from normal retinal vasculature.
Description : How does a microwave oven heat up food even though it emits no thermal radiation? -Physics
Last Answer : A microwave oven does emit thermal radiation to heat up food. Microwave radiation is thermal radiation. For some reason, most sources have a mistaken notion that thermal radiation = infrared radiation ... a broad spectrum of frequencies with a certain shape that depends on the emitter's temperature.
Description : If by mistake radioactive substance gets into human body, then from the point of view of radiation damage, the most harmful will be one that emits.
Last Answer : If by mistake radioactive substance gets into human body, then from the point of view of radiation damage, ... neutrons C. `beta`-rays D. `alpha`-rays
Description : __________ plant emits large amount of SO2 as an air pollutant. (A) Nitric acid (B) Sulphuric acid (C) Chlor alkali (D) Iron & steel
Last Answer : (B) Sulphuric acid
Description : A ?black hole? is a body in space which does not allow any radiation to come out. This property is due to its (a) Very small size (b) Very large size (c) Very high density (d) Very low density
Last Answer : Ans: ( c ) Very high density
Description : Pick out the wrong statement. (A) Heat transfer from a hot body to cold body by the emission of heat waves is called radiation (B) Filmwise condensation takes place on non-wettable surfaces (C) The ... of a solution is affected by liquid head as well as boiling point elevation (D) None of these
Last Answer : (B) Filmwise condensation takes place on non-wettable surfaces
Description : A frheshly prepared radioactive source of half life 2 hrs emits radiation of intensity which is 32 times the permissible safe value of intensity. Whic
Last Answer : A frheshly prepared radioactive source of half life 2 hrs emits radiation of intensity which is 32 times the ... B. 5hrs C. 10 hrs D. 32 hrs
Description : When a warm object is heated up why does the thermal radiation emits change?
Last Answer : Feel Free to Answer
Description : When a warm object is heated up why does the thermal radiation it emits changes?
Description : What is a neutron star which a Emits radiation that reaches the earth as radio waves and flashes of visible light?
Last Answer : pulsar
Description : Which one of the following statements is correct? (A) During the day, earth reflects solar radiation (B) During the day, earth reflects both solar radiations the emission from its surface (C) During the night, earth emits radiation from its surface (D) All of these
Last Answer : Answer: Option D
Description : Thermal radiation is an electromagnetic radiation with wavelengths in _____ range. A. 1 to 100 µm B. 0.1 to 100 µm C. 0.1 to 10 µm D. 10 to 100 µm
Last Answer : 0.1 to 100 µm
Description : In organic molecules, fluorescence seldom results from absorption of UV radiation of wavelengths lower than (A) 350 nm (B) 200 nm (C) 300 nm (D) 250 nm
Last Answer : (A) 350 nm
Description : The branch of physics that deals with the investigation of wavelengths of electro magnetic radiation emitted or absorbed by atoms is known as a) spectroscopy b) astroscopy c) radioscopy d) stereoscopy
Last Answer : a) spectroscopy
Description : When a solid material is heated, it always: w) emits a discrete radiation spectrum x) glows red y) emits a continuous radiation spectrum z) emits only visible radiation
Last Answer : ANSWER: Y -- EMITS A CONTINUOUS RADIATION SPECTRUM
Description : A black body can absorb radiations of (1) lower wavelengths only (2) intermediate wavelengths only (3) higher wavelengths only (4) all wavelengths
Last Answer : (4) all wavelengths Explanation: A black body is a theoretical object that absorbs 100% of the radiation that hits it. Therefore it reflects no radiation and appears perfectly black. At a particular ... as it must be able to absorb every wavelength to be sure of absorbing all incoming radiation.
Description : A perfectly black body: (A) Is a diffuse emitter (B) Absorbs all the radiations of every wave lengths (C) Emits power of every wave length (D) All the above
Description : A black body can absorb radiations of ; (1) lower wavelengths only (2) intermediate wavelengths only (3) higher wavelengths only (4) all wavelengths
Last Answer : all wavelengths
Description : Every hot object emits _______
Last Answer : Infrared rays
Description : Every hot object emits – (1) X-rays (2) Visible light (3) Infrared rays (4) Ultraviolet rays
Last Answer : (3) Infrared rays
Description : Every hot object emits _____ (1) X–rays (2) Visible light (3) Infrared rays (4) Ultraviolet rays
Description : . A perfect black body is a perfect __________ of radiation. (A) Absorber (B) Emitter (C) Both (A) & (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) & (B)
Description : A black body does not __________ radiation. (A) Absorb or emit (B) Refract (C) Reflect (D) Both (B) & (C)
Last Answer : (D) Both (B) & (C)
Description : The atomic number of a radioactive element is not changed, when it emits __________ rays. (A) α (B) β (C) γ (D) α & β
Last Answer : (C) γ
Description : The mass number of an element is not changed, when it emits __________ radiations. (A) α & β (B) β & γ (C) γ & α (D) α, β, & γ
Last Answer : (B) β & γ
Description : A body is called grey if the monochromatic emissivity of the body is (A) Zero (B) Unity (C) Same for all wavelengths (D) Different for all wavelengths
Last Answer : (C) Same for all wavelengths
Description : A hot body will radiate heat most rapidly, if its surface is (A) White & rough (B) Black & rough (C) White & polished (D) Black & polished
Last Answer : (B) Black & rough
Description : What must happen a substance to appear black what must happen to all wavelengths of light?
Last Answer : A substance that appears black (in a lighted room) is absorbingall of the visible light that hits it, leaving no visible light toreflect off of it to your eye. So it's absorbing visible light ... 's happening to theinfra-red or ultraviolet hitting it. For that, you need to usedifferent detectors.)
Description : When the ground gets warm it emits an invisible type of light called infrared light. This light can travel into the atmosphere and heat the air that it encounters.?
Last Answer : Some parts of the air - the so-called green-house gasses. Notthe more common parts of the air.
Description : By which of the following methods could a cup of hot coffee lose heat if placed on a metal table in a room? (a) Conduction and radiation (b) Conduction and convection (c) Convection and radiation (d) Conduction, convection, radiation and evaporation
Last Answer : Ans:(d)
Description : The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by (A) Painting the surface black (B) ... white (with aluminium paint) (C) Giving the surface a mirror finish (D) Roughening the surface
Last Answer : (B) Painting the surface white (with aluminium paint)
Description : A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun? (A) Yellow paint (B) White paint (C) Black paint (D) Grey paint
Last Answer : (C) Black paint
Description : Radiation heat losses from satisfactorily insulated high pressure boiler may be about __________ percent. (A) 1 (B) 7 (C) 18
Last Answer : (B) 7
Description : The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns. (A) 0.38-0.78 (B) 0.5-50 (C) 100-1000 (D) 5-50
Last Answer : (B) 0.5-50
Description : Heat transfer by __________ may not necessarily require the presence of a medium. (A) Conduction (B) Natural convection (C) Forced convection (D) Radiation
Last Answer : (D) Radiation
Description : Heat transfer by __________ is almost absent in case of fluidised bed drying operation. (A) Radiation (B) Conduction (C) Convection (D) Both (B) & (C)
Last Answer : A) Radiation
Description : A thin, flat & square plate measuring 2 m 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will ... heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200
Last Answer : (B) 100
Description : What is a body that emits a constant emissivity regardless of the wavelength? A. Gray body B. Black body C. Real body D. White body
Last Answer : Gray body
Description : For nearly isothermal operation involving large reaction time in a liquid-phase reaction, the most suitable reactor is a __________ reactor. (A) Stirred tank (B) Tubular flow (C) Batch (D) Fixed bed
Last Answer : (A) Stirred tank
Description : In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) (A) α = 1; ε ≠ 1 (B) α ≠ 1, ε = 1 (C) α ≠ 1, ε ≠ 1 (D) α = 1; ε = 1
Last Answer : (D) α = 1; ε = 1
Description : Which one gives the monochromatic emissive power for black body radiation? (A) Planck's law (B) Kirchhoff’s law (C) Wien's law (D) Stefan-Boltzmann law
Last Answer : (A) Planck's law
Description : The thermal radiation emitted by a body is proportional to T n , where T is its absolute temperature. The value of 'n' is exactly 4 for (A) Black painted bodies only (B) All bodies (C) Polished bodies only (D) A black body
Last Answer : (B) All bodies
Description : Pick out the correct statement. (A) Higher is the temperature of the radiating body, higher is the wavelength of radiation (B) Logarithmic mean area is used for calculating the heat flow rate ... ) Solid angle subtended by the finite surface at the radiating element is called the angle of incidence
Last Answer : (B) Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder
Description : __________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side. (A) Single pass, fixed tube sheet (B) U-tube (C) Three pass, fixed tube sheet (D) None of these
Last Answer : (B) U-tube
Description : __________ heat exchanger is used for chilling oil to be dewaxed. (A) U-tube (B) Double pipe (C) Fixed tube
Last Answer : (B) Double pipe
Description : Tube expansion allowances exist in __________ heat exchanger. (A) Multipass fixed tube sheet (B) U-tube (C) Single pass fixed tube sheet (D) None of these