All questions
- Compute the maximum radius allowed for a fiber having core refractive index 1.5 and 1.48. Answer: maximum core radius ≈ 2.35\ μm (core diameter about 4.7 µm). A step-index fibre supports only one mode if its normalised frequency (... 1
- What is a grating? Define grating element? Discuss the phenomenon of Fraunhofer’s diffraction at a grating and obtain Answer: a grating is a large number of equal, equidistant parallel slits; the grating element is (e+d) , the width of one slit plus one opaq... 1
- Discuss the phenomenon of Fraunhofer’s diffraction at a single slit and obtain the condition for the first minimum. Answer: in Fraunhofer single-slit diffraction the first minimum occurs where asinθ = λ . For the grating, the maximum order visible is 14. P... 1
- With neat energy level diagram describe the construction and working of a He-Ne Laser.
- What are different techniques to synthesize nanomaterials? Explain any one of them in detail. Answer: nanomaterials are synthesised by top-down methods (ball milling, lithography, etching, laser ablation) or bottom-up methods (sol-gel... 1
- State the advantages of optical fiber cables on conventional electrical cables Answer: optical fibres carry far more information over longer distances with lower loss, are immune to electrical interference, and are ligh... 1
- Find the divergence and curl of a vector A= x2 y î + (x-y) k ̂ Answer: nabla·vec A = 2xy and nabla×vec A = -hat i - hat j - x²hat k . Here A_x = x²y , A_y = 0 , A_z = x - y . Divergence nabla·vec A = ∂ A... 1
- Derive the expression of numerical aperture for a step index fiber. A light ray enters an optical fiber from air. Answer: NA = sqrtn₁²-n₂² . For the given fibre, critical angle ≈ 68.1^° and NA ≈ 0.568 . Derivation Let the core index be n₁ , cladding inde... 1
- Light is incident normally on a grating 0.25 cm wide with 1250 lines. Data : Number of lines / cm (N)= 5000 m=1 λ1=5895 Å λ2=5901 Å Formula : (a+b)sinθ=Nλ mN=λ/dλ Calculations : ---1 ----2 ---3 Number of lines... 2
- Explain top down and bottom up approaches to prepare nanomaterials. Answer: in the top-down approach a bulk material is broken down into nanosized pieces; in the bottom-up approach nanostructures are built up... 1
- Explain the construction and reconstruction of hologram. Answer: a hologram is made by recording, on a photographic plate, the interference pattern between laser light scattered from an object (obj... 1
- How many orders will be observed by grating having 4000 lines/cm, if it is illuminated by light of wavelength Grating equation is (a+b) sinθ =nλ , N= 4000 lines/cm For maximum orders sinθ = 1 Therefore , n_max = (a+b)/λ = 1/Nλ For 5000 Å, n_max = fra... 2
- When is a switch statement can be better than an if statement? If you have more than one condition to check on single variable or a single expression, then switch is better than if. In switch statement,... 1
- In the case of character array what is the difference b/w strlen() and sizeof() ? In character array strlen() returns the number of characters, while sizeof() returns the number of occupied bytes by character array. Exampl... 1
- What is the difference between printf() and puts() ? The function printf() writes the data on standard output device with the ability of formatted string using %c, %d, %s, %20s .. etc and print... 1
- What is a main() and difference b/w void main() and int main()? main() is an entry point ( main function) which is in most programming languages, When compiler begins compile the program, It looks for an... 1
- What is the return type of scanf() function, and what it returns ? scanf() is a library function, the prototype of scanf() is availabe in <stdio.h>, It returns a integer value, that describe successful input... 1
- What is the return type of printf() function, and what it returns ? printf() is a library function, the prototype of printf() is available in <stdio.h>, It returns a interger value, that describe how many cha... 1
- How many keywords & operators are used in c Language? There are 32 keywords & 45 operators that are used in c programming language. 1
- What is modular programming? Modular programming is a program design technique in which a large program is divided into sub programs/ functions that are called modules,... 1
- Difference b/w Entry controlled and Exit controlled loop? In Entry Controlled Loop, loop body is checked after checking the test condition i.e. condition is checked first after that loop body will e... 1
- What is fall down property? In C Programming Language, switch case statement follows the fall down property. It means when case block is executed and break statement is... 1
- Which loop statement is executed at least once even loop test condition if false? do while loop executes once even loop test condition if false. Since do while is an exit controlled loop and in this type of loop, loop body... 1
- Can we use single statement in loop body without using curly braces "{...}"? Yes, when loop body has single statement, than we can escape curly braces "...". Consider the example: Yes, when loop body has single statem... 1