The sum of reflectivity and absorptivity for an opaque body is equal to
(A) 0.5
(B) 1
(C) 0
(D) 2
Description : Absorptivity and reflectivity of a perfect black body are respectively (A) 1 and 0 (B) 0 and 1 (C) 1 and ∞ (D) 0 and 0.5
Last Answer : (A) 1 and 0
Description : For an ideal black body (A) Absorptivity = 1 (B) Reflectivity = 1 (C) Emissivity = 0 (D) Transmissivity = 1
Last Answer : (A) Absorptivity = 1
Description : For a perfectly transparent surface (like gases), the (A) Absorptivity = 0 (B) Transmissivity = 1 (C) Reflectivity = 0
Last Answer : (B) Transmissivity = 1
Description : Define the following terms : (i) absorptivity (ii) reflectivity (iii) transmissivity (iv) emissivity
Last Answer : Absorptivity: It is the fraction of total incident radiation which is absorbed by a body. Reflectivity: It is the fraction of total incident radiation which is reflected by a body. Transmissivity: It ... total emissive power of a body to emissive power of a black body at the same temperature.
Description : The absorptivity of a body is equal to its emissivity (A) At a particular temperature (B) For circular bodies (C) Under thermal equilibrium (D) None of these
Last Answer : (C) Under thermal equilibrium
Description : What is the absorptivity of a black body? (A) 1 (B) 0 (C) 0.78 (D) 0.95
Last Answer : (A) 1
Description : What is the absorptivity of a black body? A. 0 B. 1 C. 0.5 D. 0.25
Last Answer : 1
Description : Define: i. Transmissivity ii. Black body iii. Grey body iv. Reflectivity
Last Answer : Transmissivity: It is the the fraction of energy which is transmitted through the body. Or The ratio of amount of energy transmitted to the amount of energy incident on a body. Black body: A ... is defined as the ratio of amount of energy reflected to the amount of energy incident on a body.
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 : Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity? (A) Aluminium foil (B) Refractory bricks (C) Iron plate (D) Coke breeze
Last Answer : (D) Coke breeze
Description : The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoff’s law. (A) Wavelength of radiation (B) Nature of the body (C) Temperature of the body (D) None of these
Last Answer : (C) Temperature of the body
Description : Pick out the wrong statement: (A) With change in temperature, the radiant energy emitted by a black body remains unchanged (B) Absorptivity of a body approaches unity in case of diffuse reflection (C) Absorptivity of ... unity (D) Value of Stefan-Boltzmann constant is 4.876 10 -8 KCal/m2 .hr.°K4
Last Answer : (A) With change in temperature, the radiant energy emitted by a black body remains unchanged
Description : The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation. (A) Increases (B) Decreases (C) Remain constant (D) May increase or decrease; depends on the material
Last Answer : (D) May increase or decrease; depends on the material
Description : What states that for any two bodies in thermal equilibrium, the ratios of emissive power to the absorptivity are equal? A. Kirchhoff’s radiation law B. Newton’s law of cooling C. Stefan-Boltzmann law D. Hess’s law
Last Answer : Kirchhoff’s radiation law
Description : What refers to the rate of thermal radiation emitter per unit area of a body? A. Thermal conductivity B. Absorptivity C. Emissivity D. Emissive power
Last Answer : Emissive power
Description : The changes in the reflectivity/emissivity with time, is called: (A) Spectral variation (B) Spatial variation (C) Temporal variation (D) None of these
Last Answer : Answer: Option C
Description : A reduction of nitrogen nutrient in plants: (A) Affects leaf colour (B) Reduces pigment concentration (C) Increase the visible reflectivity (D) All of these
Last Answer : Answer: Option D
Description : Which one of the following is not a matter a global concern in the removal of tropical forests ? (A) Their ability to absorb the chemicals that contribute to depletion of ozone layer ... , moisture content and reflectivity. (D) Their contribution to the biological diversity of the planet.
Last Answer : (A) Their ability to absorb the chemicals that contribute to depletion of ozone layer.
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 : Which of the following has the minimum absorptivity? (A) Aluminium foil (B) Coal dust (C) Refractory bricks (D) Iron plates
Last Answer : (A) Aluminium foil
Description : The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium". This is __________ law. (A) Kirchoff’s (B) Planck's (C) Wien's displacement (D) Stefan-Boltzmann
Last Answer : (A) Kirchoff’s
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 : Where can I find a small, opaque, hermetically sealed jar?
Last Answer : Do you really mean hermetically sealed, or do you just mean stoppered?
Description : Why do the opaque gummies always taste better?
Last Answer : This is such a shallow question, I can see right through it ;¬} Oh & yeah, I happen to agree.
Description : When I shoot tap water at home, it's opaque for a while and it's transparent after a while, is that normal?
Last Answer : Yes, it is completely normal for water networks. You don't have to worry.
Description : When I put a flower in a transparent container, it won't grow?
Last Answer : I also grew peppers in a transparent pot and there is no problem with that. ;-)
Description : Which of the following is opaque?
Last Answer : Which of the following is opaque? A. Water B. Glass C. Mirror D. Prism
Description : Is a diamond opaque?
Last Answer : What is the answer ?
Description : Is a tv opaque?
Last Answer : Need answer
Description : When light strikes an opaque material accurately describes what happens to the light rays?
Description : Can fiber optic cable be used for transmitting light from a source to another point around the opaque object?
Last Answer : Fiber Optic is normally used for carrying data as light; I doubt it'd be useful for actually transmitting coherent light.
Description : A ray of white light strikes the surface of an object. If all the colours are reflected, the surface would appear (1) Black (2) White (3) Grey (4) Opaque
Last Answer : (2) White Explanation: Objects do not have any colour of their own. When light hits a surface, some of it is absorbed and some of it is reflected. The light that is reflected is ... appear white when they reflect all the wavelengths; they appear black when they absorb all visible wavelengths.
Description : The dwarfing gene in rice is: (A) Opaque – 2 (B) Tift – 23 A (C) Dee – Gee – Woo – Gen (D) Norin -10
Last Answer : (C) Dee – Gee – Woo – Gen
Description : When information is transformed from a useful form of understanding to an opaque form of understanding, this is called: a) Encryption b) Decryption c) Both of Above d) None of These
Last Answer : a) Encryption
Last Answer : c) Both of Above
Description : The message in pub/sub is an opaque blob of ________ a) Bits b) Bytes c) Word d) Nibble
Last Answer : Bytes
Description : For sanitary pipes and chemical stonewares, (A) Salt glazing is used (B) Lead glazing is used (C) Opaque glazing is used (D) None of these
Last Answer : Answer: Option A
Description : “Pop off” of a porcelain veneer from the under the lying gold crown is due to:** A. Too thick application of pure gold surface conditioner B. Contamination at the porcelain metal interface C. Under firing the opaque layer D. All of the above
Last Answer : B. Contamination at the porcelain metal interface
Description : When should metallic framework not be contaminated during the fabrication of a porcelain fused to metal crown: A. Between bisque stage and glazing stage B. Between preheat and opaque stages C. Between opaque and bisque stages D. Between one opaque and two opaque stages
Last Answer : B. Between preheat and opaque stages
Description : Porcelain must not be contaminated by handling between which two stages: A. Pre-soldering and heat treatment B. Heat treatment and opaque /bake/ stages C. Opaque and bisque stages D. Bisque and glazing stages E. First opaque bake and second opaque bake
Last Answer : A. Pre-soldering and heat treatment
Description : What is NOT characteristic of root canal filing materials (“obturation material”) A. Tacky adhesive to walls B. Radio opaque C. Not irritating D. Quick in setting
Last Answer : D. Quick in setting
Description : Fraunhofer diffraction at a Plane Grating What is the meaning of grating element for a diffraction grating? A It is the width of a single slit B. It is the width of the opaque space C. It is the distance between two slits D. It is the width of diffraction grating
Last Answer : C. It is the distance between two slits
Description : What term is used to describe the procedure whereby a catheter is inserted into an individual's heart, a radio-opaque medium is injected, and x-ray images are made. The procedure is used to locate wher arteries are blocked and the degree to which the blockage has developed.
Last Answer : ANSWER: Angiography or Angiogram
Description : Frame the formula: final velocity (v) of a body in linear motion is equal to the sum of its initial velocity (u) and the product of acceleration (a) a
Last Answer : Frame the formula: final velocity (v) of a body in linear motion is equal to the sum of its initial velocity (u) and ... v=u-at C. v=u+at D. v=-u-at
Description : For a body to be in equilibrium, which of the following conditions must exist? w) no forces may be acting on the body. x) the body must be accelerating. y) the velocity of the body must be zero. z) the sum of the forces acting on the body must be equal to zero.
Last Answer : ANSWER: Z -- THE SUM OF THE FORCES ACTING ON THE BODY MUST BE EQUAL TO ZERO.
Description : The sum of the shape function is equal to a.0 b.0.5 c.1 d.2
Last Answer : c.1
Description : Rahul got next chance. What is the probability that he got the sum of the two numbers appearing on the top face of the dice is equal to 7? a. 5/9 b. 5/36 c. 1/6 d. 0
Last Answer : c. 1/6
Description : Now it was Ravi‘s turn. He rolled the dice. What is the probability that he got the sum of the two numbers appearing on the top face of the dice is less than or equal to 12? a. 1 b. 5/36 c. 1/18 d. 0
Last Answer : a. 1
Description : If the sum of the roots of the equation ax^2 + bx + c = 0 is equal to the sum of their squares, then which one of the following is correct ? -Maths 9th
Last Answer : Given equation: ax2+bx+c=0 Let α and β be the roots of given quadratic equation Sum of the roots i.e. α+β=a−b Product of roots i.e. αβ=ac It is given that, Sum of the roots = Sum of squares of the roots i ... )2−2αβ i.e. a−b =(a−b )2−a2c i.e. −ab=b2−2ac i.e. ab+b2=2ac Hence, C is the correct option.
Description : If the sum of all the solutions of the equation `8 cosx.(cos(pi/6+x)cos(pi/6-x)-1/2)=1` in `[0,pi]` is `k pi` then k is equal to
Last Answer : If the sum of all the solutions of the equation `8 cosx.(cos(pi/6+x)cos(pi/6-x)-1/2)=1` in `[0,pi]` is `k pi` ... (20)/(9)` C. `(2)/(3)` D. `(13)/(9)`