GATE  >  Absorptivity, Reflectivity, and Transmissivity - GATE

Absorptivity, Reflectivity, and Transmissivity - GATE Notes - GATE

Document Description: Absorptivity, Reflectivity, and Transmissivity - GATE for GATE 2022 is part of GATE preparation. The notes and questions for Absorptivity, Reflectivity, and Transmissivity - GATE have been prepared according to the GATE exam syllabus. Information about Absorptivity, Reflectivity, and Transmissivity - GATE covers topics like and Absorptivity, Reflectivity, and Transmissivity - GATE Example, for GATE 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Absorptivity, Reflectivity, and Transmissivity - GATE.

Introduction of Absorptivity, Reflectivity, and Transmissivity - GATE in English is available as part of our GATE preparation & Absorptivity, Reflectivity, and Transmissivity - GATE in Hindi for GATE courses. Download more important topics, notes, lectures and mock test series for GATE Exam by signing up for free. GATE: Absorptivity, Reflectivity, and Transmissivity - GATE Notes - GATE

For an opaque surface, the absorptivity (α), transmissivity (τ) and reflectivity (ρ) are related by the equation:
  • a)
    α + ρ = τ
  • b)
    α + ρ + τ = 0
  • c)
    α + ρ = 1
  • d)
    α + ρ = 0
Correct answer is option 'C'. Can you explain this answer?

Ref: https://edurev.in/question/579878/For-an-opaque-surface-the-absorptivity-alpha-t

1 Crore+ students have signed up on EduRev. Have you?

Absorptivity, Reflectivity, and Transmissivity

Everything around us constantly emits radiation (for heat transfer), and the emissivity represents the emission characteristics of those bodies.

This means that every body, including our own, is constantly bombarded by radiation coming from all directions over a range of wavelengths.

Coming directly to our topic let us discuss each term one by one.


Irradiation

The radiation flux incident on a surface is called irradiation and is denoted by G.

Absorptivity, Reflectivity, and Transmissivity - GATE Notes - GATE
                                                                                      Fig.1

When radiation strikes a surface, part of it is absorbed, part of it is reflected, and the remaining part, if any, is transmitted, as illustrated in Figure (1).


Absorptivity

The fraction of irradiation absorbed by the surface is called the absorptivity α,

Reflectivity

The fraction of radiation reflected by the surface is called the reflectivity ρ,

Transmissivity

The fraction of radiation transmitted is called the transmissivity τ.

That is,

Absorptivity, Reflectivity, and Transmissivity - GATE Notes - GATE

Where is the radiation energy incident on the surface, and Gabs, Gref, and Gtr are the absorbed, reflected, and transmitted portions of it, respectively.

The first law of thermodynamics requires that the sum of the absorbed, reflected, and transmitted radiation energy be equal to the incident radiation. That is,

Gabs + Gref + Gtr = G

Dividing each term of this relation by yields

α+ρ+τ=1

For opaque surfaces, τ=0, and thus

α+ρ=1

This is an important property relation since it enables us to determine both the absorptivity and reflectivity of an opaque surface by measuring either of these properties.

The document Absorptivity, Reflectivity, and Transmissivity - GATE Notes - GATE is a part of GATE category.
All you need of GATE at this link: GATE
Use Code STAYHOME200 and get INR 200 additional OFF
Use Coupon Code
Download as PDF

Download free EduRev App

Track your progress, build streaks, highlight & save important lessons and more!

Related Searches

and Transmissivity - GATE Notes - GATE

,

Exam

,

and Transmissivity - GATE Notes - GATE

,

Reflectivity

,

Summary

,

Reflectivity

,

Objective type Questions

,

Absorptivity

,

practice quizzes

,

Previous Year Questions with Solutions

,

Absorptivity

,

Extra Questions

,

mock tests for examination

,

Reflectivity

,

Free

,

pdf

,

Absorptivity

,

MCQs

,

ppt

,

and Transmissivity - GATE Notes - GATE

,

shortcuts and tricks

,

past year papers

,

study material

,

video lectures

,

Sample Paper

,

Important questions

,

Semester Notes

,

Viva Questions

;