Thermal Radiation Discover how heat travels through space without a medium in this Thermal Radiation Quiz!Learn about black bodies, emissivity, Stefan–Boltzmann law, Kirchhoff’s law, and view factors in a fun, practical way. This quiz helps you visualize how real surfaces absorb, emit, and exchange energy — a must-know topic for every mechanical engineer aiming to master Heat Transfer fundamentals. 1 / 20 Radiation heat transfer dominates at High temperature Low temperature Medium temperature Zero temperature difference At high temperatures, radiative effects become more significant than conduction or convection. 2 / 20 When two surfaces have same temperature and emissivity, the net radiation between them is Zero Maximum Minimum Constant No temperature difference means no net heat exchange. 3 / 20 The ratio of radiative heat flux from a surface to that from a black body at same temperature is Emissivity Absorptivity Reflectivity Shape factor Emissivity represents actual radiation relative to black body. 4 / 20 Radiation shields are used to Enhance reflection Reduce heat transfer Increase emissivity Increase temperature Shields minimize radiation exchange by lowering view factor. 5 / 20 According to Wien’s law, the product of wavelength and temperature is Zero Inversely proportional Directly proportional Constant λmaxT=Constant 6 / 20 The wavelength corresponding to maximum emissive power is given by Newton’s Law Kirchhoff’s Law Wien’s Law Fourier’s Law Wien’s law relates temperature and wavelength of peak emission. 7 / 20 A grey body is one which Reflects all incident radiation Absorbs all radiation Does not emit any radiation Has emissivity less than one but constant Grey body emits a fixed fraction of black body radiation at all wavelengths. 8 / 20 The radiation emitted per unit area of a black body is proportional to Square of temperature Temperature difference Inverse of temperature Fourth power of absolute temperature 9 / 20 The emissivity of polished surfaces is generally Low High Equal to one Constant Smooth and shiny surfaces reflect more and emit less heat. 10 / 20 Radiation heat transfer does not require Solid body Liquid Gas Any medium Radiation can occur in vacuum, unlike conduction or convection. 11 / 20 The net radiation heat exchange between two bodies depends on Their temperatures and emissivity's Their densities Only surface area Only distance Heat exchange rate is determined by temperature difference and surface properties. 12 / 20 The shape factor is also known as View factor Radiation angle Transmission ratio Reflectivity It defines the fraction of radiation leaving one surface that strikes another. 13 / 20 Kirchhoff’s law of radiation states that Emissivity is always zero Good absorbers are good emitters Good conductors are bad emitters Radiation is independent of temperature Absorptivity equals emissivity for a body in thermal equilibrium. 14 / 20 The Stefan–Boltzmann constant value is approximately 1.23 × 10⁻⁶ W/m²·K 5.67 × 10⁻⁸ W/m²·K⁴ 6.62 × 10⁻³ J/m²·K 9.81 × 10⁻⁵ W/m²·K² It’s the proportionality constant in Stefan–Boltzmann law. 15 / 20 Stefan–Boltzmann law gives the relation between Emissive power and temperature Conductivity and area Convection coefficient and velocity Pressure and density It states that total emissive power ∝ T⁴. 16 / 20 The emissivity of a perfect black body is 0 0.5 0.9 1 A black body has maximum emissivity value of one. 17 / 20 A perfect black body absorbs No radiation Only visible light Only infrared rays All incident radiation A black body absorbs 100% of the radiation falling on it. 18 / 20 The unit of emissive power is W/m³ W/m² W/m·K J/m²·s It measures energy emitted per unit area per second. 19 / 20 The speed of thermal radiation is equal to Depends on temperature Twice the speed of light Speed of sound Speed of light Radiation energy travels at the same speed as light in vacuum. 20 / 20 Thermal radiation is the transmission of heat through Electromagnetic waves Conduction Convection Physical contact Radiation transfers heat without any medium via electromagnetic waves. Your score isThe average score is 0% 0% Restart quiz
