Numerical Problems Chapter 9 Physical Optics l First Year Physics KPK Syllabus

1. In young double slit experiment the separation of the slits is 1mm and red light of wavelength 620nm is falling on it. Determine the distance between the central bright band and the fifth bright fringe on the screen which is 3m away from the slit.
2. Two parallel slits are illuminated by light of two wavelengths, one of which is 5.8×〖10〗^(-7) m. On the screen the fourth dark line of the known wavelength coincides with the fifth bright line of the light of unknown wavelength. Find the unknown wavelength.
3. When the movable mirror of a Michelson interferometer is moved 0.1mm. How many dark fringes pass through the reference point, if light of wavelength 580nm is used?
4. A soap film has a refractive index of 1.40. How thick must the film be, if it appears black, when mercury light of wavelength 546.1nm falls on it normally?
5. A diffraction grating has 5000 lines per centimeter. At what angle does the second order spectrum of the sodium yellow light of wavelength 589nm occur?
6. Light is incident normally on a grating which has 250 lines/mm. Find the wavelength of spectral line for which the deviation in second order is 12o.
7. In a certain X-rays diffraction experiment the first order image is observed at an angle of 5o for a crystal plane of spacing of 2.8×10-10m. What is the wavelength of X-rays used?
8. An X-ray beam of wavelength 0.48×10-10m is used to get Bragg reflection from a crystal at an angle of 20o for the first order maximum. What are the possible layer plane spacing which give rise to this maximum?
9. The spacing of one set of crystal planes is NaCl (table salt) is d=0.282nm. A monochromatic beam of X-rays produces a Bragg maximum when its glancing angle with these planes is θ=7°. Assuming that this is a first order maximum (n=1), find the wavelength of the X-rays.

[physicswithshehryar]

Dear buddy, while solving question no:2, you placed m=3 in the dark fringe equation which makes the answer wrong. The correct value of m is 4, as it is clearly said in the question. The correct answer is 5.2 * 10^(-7) m.
Similarly in the third question, the distance at which the mirror is moved is 0.1 mm, not 0.01 mm.

[aseelshauqbywaiz]

Thankyou so much Sir G.It is amazing lecture.

[raoatiq]

Aoa sir
Aap k lectures sy aik average student like me koi faida nhi horha aap bht alg smjhaty hn mujhy aapki blkul smjh nhi aati lec kxh is trah sy record krein k aap bolein to hmein pta ho Kia bol rhy h aapka bolna waste na jye itni mhnt sy ap lec. Rec krty hn to sir plz iss mhnt thodi or mhnt shamil kr k inhein mzeed bhtr bnayie taa. K hr bnda achy sy mustfeed hosky tnx u💞

[waleedabbasi]

Sir the way of teaching is so good.. 👍👌

[BestFriends-wnzr]

SIR REALLY APPRECIATING YOUR EFFORTSSS ❤❤❤❤❤

[abbasjadoon]

Sir can u tell me why u have used( 3 )for y4 th dark fringe
Plzz

[Affan]

Sir ji numericals tora detail mai samjaia krain ap bohat taiz taiz krwata hai . Aj ki samaj aagai lakin ch 8 kai numericals ki nahi ai❤

[reyodgk]

Sir how you take the value of m 3 for fourth dark fringe in q no 2

[ahmedbinalamin]

Sir numerical #3 answer is not coming correctly its 34.5

[beautifulvideos]

Aoa sir numerical no. 2 ka answer ghalat hai. book mai koi or answer likha hai. Can you explain me?😠😨🥺😳

[moonff]

Sir Q5 ka to book mai answer 0.36 hai aap ka 36 aaya hai

[chashmuno]

Sir 4th numerical main formula destructive interference ye tou nai hota

[hamdan]

Sir isi chapter k assignments chahiye...plz upload kar den...

[itsM.T]

Video beshak zayada time ki ho gay har cheez ko Sahi Tarah explain to karain na please ....

[UsamaKhan-zxyf]

Assalamualaikum sir in question no 5 answer is 0.36 but your answer is 36 how

[basitkhvn]

Aoa not hating or something but aap bas wohi batate hain jo screen pe likha hua ha .. koi value kahen kiun lag rahi ha aur kaise lag rahi please ye bhe batadia karen aise he slides dekh ke parhana ka to phr hamen koi faida na hua .. hope you will take it as constructive criticism

[wazir]

Numerical no 2 wala answer tau book wale answer sai kafi different hay

[haniaaa]

Sir the value for nomerical number 7 and 8 I'm putting same like yours but my answer is coming something different

[incognito__]

Assalam o alaikum sir,
Thank a million for this video!👑✨
But sir I wanted to ask you that from where we get to know that "n" in question no.2. like...not the value, I'm asking about that 2nx

[songswings]

2 numerical ka answer same ni Aya ? Sir