Description : Higher concentration of CO2 in atmosphere (A) Allows visible solar radiation (ultraviolet) of short wave-length to pass through (B) Reflects and absorbs the longer wavelength (infra-red) radiations (C) Prevents solar heat being ... in 'heat trap' i.e., global warming (D) All (A), (B) and (C)
Last Answer : (D) All (A), (B) and (C)
Description : The increasing amount of CO2 in the atmosphere is slowly raising its temperature because it absorbs (a) the infrared part of the solar radiation (b) the ultraviolet part of the solar radiation (c) all the solar radiations (d) the water vapour of the air
Last Answer : Ans:(a)
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
Last Answer : Answer: Option D
Description : Ozone layer in the outer atmosphere helps us in – (1) reflecting radio waves and makes radio communication possible (2) regulating he temperature of atmosphere (3) absorbing cosmic ray particles (4) absorbing U-V radiations
Last Answer : (4) absorbing U-V radiations Explanation: The ozone layer is a layer in Earth's atmosphere containing relatively high concentrations of ozone (03) which absorbs 97- 99% of the Sun's medium-frequency ultraviolet light.
Description : Ozone layer in the outer atmosphere helps us in (1) reflecting radio waves and makes radio communication possible (2) regulating the temperature of atmosphere (3) absorbing cosmic ray particles (4) absorbing U-V radiations
Last Answer : absorbing U-V radiations
Description : A body absorbs heat most if it is – (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth
Last Answer : (1) black and rough Explanation: A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. Another property is roughness. Sand is rough and black and so it is a good absorber.
Description : A body absorbs heat most if it is (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth
Last Answer : black and rough
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
Description : In a laboratory test run, the rate of drying was found to be 0.5 x 10 - 3 kg/m2 .s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry ... of the solids from 0.3 to 0.2 (dry basis) is (A) 2000 (B) 4000 (C) 5000 (D) 6000
Last Answer : (C) 5000
Description : Pick out the wrong statement. (A) Economy of a multiple effect evaporator is not influenced by the boiling point elevation (B) Two identical cubes of iron and copper will have the same heat ... in the field of refrigeration (D) Finned tube heat exchangers are suitable for heating air by steam
Last Answer : (B) Two identical cubes of iron and copper will have the same heat content under the same conditions of temperature
Description : Which among the following colures absorbs more radiation? (A) Blue (B) Black (C)Red (D) White
Last Answer : (B) Black
Description : Pick out the wrong statement. (A) The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation ( ... in a heat exchanger is controlled by the value of the film co-efficient, which is higher
Last Answer : (D) Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film co-efficient, which is higher
Description : An object which absorbs all colours and reflects none appears: (1) White (2) Grey (3) Blue (4) Black
Last Answer : (4) Black Explanation: A surface that absorbs all colours, reflecting none, is said to be black. Black is not a colour; it absorbs all the colours of the visible spectrum and reflects none of them to the eyes. White is a colour.
Description : An object which absorbs all colours and reflects none appears: (1) white (2) grey (3) blue (4) black
Last Answer : black
Description : Which surface absorbs all forms of light and heat?
Last Answer : black surface
Description : It is dangerous to observe solar eclipse with naked eyes because – (1) Infrared radiations from sun burn our retina (2) Ultraviolet radiations from Sun burn our retina (3) All radiations from sun initiate chemical reactions in eyes (4) Cosmic rays reach eyes more during the eclipse
Last Answer : (2) Ultraviolet radiations from Sun burn our retina Explanation: The solar radiation that reaches the surface of Earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio ... of the Sun during an eclipse is for the development of "eclipse blindness" or retinal burns.
Description : It is dangerous to observe Solar eclipse with naked eyes because (1) Infrared radiations from sun burn our retina (2) Ultraviolet radiations from Sun burn our retina (3) All radiations from sun initiate chemical reactions in eyes (4) Cosmic rays reach eyes more during the eclipse
Last Answer : Ultraviolet radiations from Sun burn our retina
Description : Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants? (a) Blue and green (b) Green and red (c) Red and violet (d) Violet and blue
Last Answer : (d) Violet and blue
Description : With identical beam and column, buckling occurs as compared to bending under a (a) Lesser load (b) Larger load (c) Equal load (d) None
Last Answer : (a) Lesser load
Description : The concept of chemical evolution is based on (a) interaction of water, air and clay under intense heat (b) effect of solar radiation on chemicals (c) possible origin of life by combination of chemicals under suitable environmental conditions (d) crystallisation of chemicals.
Last Answer : (c) possible origin of life by combination of chemicals under suitable environmental conditions
Description : The centre of the reflecting surface of a spherical mirror is called the : (1) Radius (2) Centre of Curvature (3) Pole (4) Focus
Last Answer : (3) Pole Explanation: The center of the reflecting surface of a spherical mirron is called as the pole of the mirror which is mainly known as the center of curvature.
Description : The term dispersion describes the process of ∙ A. separating light into its component frequencies ∙ B. reflecting light from a smooth surface ∙ C. the process by which light is absorbed by an uneven rough surface ∙ D. light scattering
Last Answer : A. separating light into its component frequencies
Description : The termdispersion describestheprocessof a.separatinglightinto its componentfrequencies b. reflecting light from a smooth surface c. the process by which light is absorbed by an uneven rough surface d. light scattering
Last Answer : a.separatinglightinto its componentfrequencies
Description : What reflecting surface forms a geometrically perfect image of a point source located at infinity (such as that approximated by a star)? w) Paraboloid x) Ellipsoid y) spherical z) Hyperboloid
Last Answer : ANSWER: W -- PARABOLOID
Description : According to standard convention, the angles of incidence and reflection for a plane surface are measured from: w) the reflecting surface x) lines at 45 degrees to the reflecting surface y) a line at 90 degrees to the reflecting surface z) there is no standard
Last Answer : ANSWER: Y -- A LINE AT 90 DEGREES TO THE REFLECTING SURFACE
Description : Assume a ray of light is incident on a smooth reflecting surface at an angle of incidence of 15 degrees to the normal. What is the angle between the incident ray and the reflected ray?
Last Answer : ANSWER: 30 DEGREES
Description : Metal are good conductors, because (1) they contain free electrons (2) the molecules in them are very close to each other (3) the molecules in them collide very freely (4) they contain reflecting surface
Last Answer : they contain free electrons
Description : Solar cooker takes more time as compared to the LPG to boil potato or rice, yet Kunal uses solar cooker for such type of cooking: (i) Why does Kunal uses Solar cooker instead of LPG? ... answer. (ii) Name the phenomenon which is responsible for obtaining high temperature in solar cooker. -Science
Last Answer : (a)(i) There are no energy losses while cooking on the solar cooker as the food gets cooked in a controlled environment whereas cooking on the LPG leads to maximum percentage of energy loss. ( ... saves a lot of prestigious time which is normally consumed for cooking purpose. (b) Greenhouse effect.
Description : The efficiency of two identical transformers under load conditions can be determined by?
Last Answer : The efficiency of two identical transformers under load conditions can be determined by back-to-back test.
Description : Air over the oceans is colder in summer and warmer in winter compared with air over the continental regions. This is because (a) Water is translucent and has a relatively high heat capacity compared ... B are true (e) The effect is due to the changes in circulation between continents and oceans
Last Answer : (d) Both A and B are true
Description : Which of the following is generally considered as opaque surface towards radiations? (A) Gases (B) Solids (C) Liquids (D) Both (B) and (C)
Last Answer : (D) Both (B) and (C)
Description : Rate of low temperature oxidation of coal due to bad storage conditions (A) Decreases with increase in surface area (B) Does not vary with increase in surface area (C) Is more for low volatile ... to high volatile coal (D) Is accelerated by storage in large heaps with small surface to volume ratio
Last Answer : (D) Is accelerated by storage in large heaps with small surface to volume ratio
Description : Which of these radiations is used to study the black hole? -Space
Last Answer : When our eyes look at the heavens we see the visible light from stars and other objects in the Universe. Thousands of years ago astronomers in Greece and other ancient cultures already built a detailed ... . We encounter radio waves often in our daily lives, for example in radios and cell phones.
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 : At the Highest value of black body radiations, it wavelength –
Last Answer : Decreases with increasing temperature
Description : Black body radiations depends upon a) The shape and nature of the body b) The velocity of radiations and colour of the body c) The temperature of the body d) All of the above
Last Answer : c) The temperature of the body
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 : EPROM contents can be erased by exposing it to (A) Ultraviolet rays. (B) Infrared rays. (C) Burst of microwaves. (D) Intense heat radiations.
Last Answer : (A) Ultraviolet rays. EPROM contents can be erased by exposing it to Ultraviolet rays (The Ultraviolet light passes through a window in the IC package to the EPROM chip where it releases stored charges. Thus the stored contents are erased).
Description : The water in an open pond remains cool even in hot summer because (a) Of continuous evaporation of water (b) Water radiates heat more rapidly than the atmosphere (c) Water absorbs heat less rapidly than the atmosphere (d) Water absorbs heat more rapidly than the atmosphere
Last Answer : Ans:(c)
Description : An iron hammer, lying in the sun, appears much hotter than its wooden handle because (a) iron is at a higher temperature (b) iron is darker than wood (c) iron absorbs more heat (d) iron is a good conductor of heat
Last Answer : Ans:(d)
Description : Pick out the wrong statement. (A) In process heat exchangers, saturated steam is preferred over the superheated steam (B) The maximum is the emissive power of a surface at a temperature T1 ... under natural convection conditions, the velocity profile in air, normal to the plate, exhibits a maximum
Last Answer : (B) The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1 . If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 λ1
Description : Equal masses of oxygen, hydrogen and methane are taken in a container in identical conditions. Find the ratio of their moles.
Last Answer : Equal masses of oxygen, hydrogen and methane are taken in a container in identical conditions. Find the ratio of their ... 1 : 8` D. `16 : 1 : 8`
Description : List down various types of clamping devices used in design of Jigs. Explain any one with sketch.
Last Answer : List of Types of clamping devices used in design of jigs. i. Screw clamp ii. Pivoted clamp. iii. Equalizing clamp. iv. Latch clamp. v. Wedge clamp. vi. Hinged jaw clamp. ... to be gripped on its edges as shown in figure. This arrangement ensures easy machining of the work piece
Description : Soap helps in better cleaning of clothes because - (1) Soap acts like catalyst (2) It reduces the surface tension of solution (3) It gives strength to solution (4) It absorbs the dirt
Last Answer : (2) It reduces the surface tension of solution Explanation: Soaps are effective cleaners because they can dissolve and the oil and grease that holds dirt in place. They reduce the surface tension of the ... surfactant molecules help water to get a hold of grease, break it up, and wash it away.
Description : An egg sinks in soft water but floats in a concentrated solution of salt because – (1) Egg absorbs salt from the solution and expands (2) Albumin dissolves in salt solution and egg becomes lighter (3) The density of salt solution exceeds the density of eggs (4) Water has high surface tension
Last Answer : (3) The density of salt solution exceeds the density of eggs Explanation: Following the density principle, the density of the egg compared to the density of the tap water is lesser (the density principle ... and that is why an egg sinks in soft water but floats in a concentrated solution of salt.
Description : A considerable part of the harmful ultraviolet radiation of the sum does not reach the earth surface, because of the fact that, there is a layer of __________ high above earth's atmosphere, which absorbs it. (A) Hydrogen (B) Carbon dioxide (C) Ozone (D) None of these
Last Answer : (C) Ozone
Description : Soap helps in better cleaning of clothes because (1) Soap acts like catalyst (2) It reduces the surface tension of solution (3) It gives strength to solution (4) It absorbs the dirt
Last Answer : It reduces the surface tension of solution
Description : An egg sinks in soft water but floats in a concentrated solution of salt because (1) egg absorbs salt from the solution and expands (2) albumin dissolves in salt solution and egg becomes lighter (3) the density of salt solution exceeds the density of eggs (4) water has high surface tension
Last Answer : the density of salt solution exceeds the density of eggs
Description : Which one of the following statements is correct ? a) For water at 100o Celsius at sea level, the vapour pressure is equal to atmospheric pressure b) Surface energy (or tension) is caused by ... it both in static and in dynamic conditions d) Air is 50,000 times more compressible than water
Last Answer : c) Viscosity of a fluid is the property exhibited by it both in static and in dynamic conditions