1. |
Which one of the following constants is not related to radiation? (a) Solar constant (b) Stefan’s constant (c) Boltzmann’s constant (d) Wien’s constant |
Answer: (c) |

2. |
Rate of cooling of body is 0.5°C/min, when the system is 50°C above the surroundings. When a system is 30°C above the surroundings, the rate of cooling will be
(a) 0.3°C/min (b) 0.6°C/min (c) 0.7°C/min (d) 0.4°C/min |
Answer: (a) |

3. |
The sun emits light with a maximum wavelength of 510 nm while another star X emits light of maximum wavelength of 350 nm. What is the ratio of the surface temperatures of the sun and the star? (a) 0.35 (b) 1.5 (c) 1.1 (d) 0.69 |
Answer: (d) |

4. |
A sphere cube and a thin circular plate all made of the same material and having the same mass are initially heated to a temperature of 300°C. which of these cools fastest? (a) Sphere (b) Cube (c) Plate (d) None of these |
Answer: (c) |

5. |
An extremely hot star would appear to be (a) Yellow (b) Orange (c) Blue (d) Red |
Answer: (c) |

6. |
A body at higher temperature T°K radiates heat at a rate which is proportional to (a) T (b) T (c) T (d) T |
Answer: (d) |

7. |
A black body emissive power is 81 J/m (a) 200 J/m (b) 300 J/m (c) 400 J/m (d) 500 J/m |
Answer: (d) |

8. |
Which one of the following constants is related to radiation? (a) Gravitational constant (b) Planck’s constant (c) Critical constant (d) Boltzmann’s constant |
Answer: (b) |

9. |
If a black body is heated from 27°C to 927°C. then the ratio of radiation emitted will be (a) 1: 4 (b) 1: 16 (c) 1: 8 (d) 1: 256 |
Answer: (d) |

10. |
You are given a sphere, a cube and a thin circular plate, all made from copper and all having the same mass. If they are heated to a temperature of 200°C, then which are of them will cool fasted? (a) Sphere (b) Thin circular plate (c) Cube (d) All at the same rate |
Answer: (b) |

11. |
For a given body at a particular temperature, its coefficients of reflection and transmission are 0.63 and 0.21 respectively. Then its coefficient of emission at the same temperature will be (a) 0.16 (b) 0.32 (c) 0.84 (d) 0.36 |
Answer: (a) |

12. |
The unit of Stefa’s constant is (a) watt/m (b) watt/m (c) watt/m (d) watt/m |
Answer: (a) |

13. |
A body of surface area 25 × 10 (a) 0.5 Kcal/m (b) 0.6 Kcal/m (c) 0.7 Kcal/m (d) 0.8 Kcal/m |
Answer: (d) |

14. |
The wavelength of maximum energy release during an atomic explosion was 2.93 × 10 (a) 5.86 × 10 (b) 10 (c) 10 (d) 10 |
Answer: (d) |

15. |
The solar constant for the earth is about 1.8 J/m (a) 9 J/m (b) 12 J/m (c) 15 J/m (d) 20 J/m |
Answer: (d) |

16. |
Emissivity of perfectly black body is (a) 1 (b) 2 (c) 5 (d) 0 |
Answer: (a) |

17. |
The velocity of thermal radiation (V) is related to the velocity of light (C) as (a) V > C (b) V < C (c) (d) V = C |
Answer: (d) |

18. |
If a = 0.72, r = 0.24, then value of t is
(a) 0.02 (b) 0.04 (c) 0.4 (d) 0.2 |
Answer: (b) |

19. |
Wien’s constant units is (a) m.k (b) kg (c) m.m (d) mg. |
Answer: (a) |

20. |
A liquid takes 5 minutes to cool from 80°C to 50°C. how much time it will take to cool from 60°C to 30°C, if the temperature of the surrounding is 20°C? (a) 5 minutes (b) 7 minutes (c) 9 minutes (d) 12 minutes |
Answer: (c) |