In a hydrogen atom a transition of electrons take place from 3rd
    • Zigya Logo

    Subject
    Physics

    Class

    ICSE Class 12

    Pre Boards

    Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

    Sample Papers

    Download the PDF Sample Papers Free for off line practice and view the Solutions online.
    Advertisement

    ISC Class 12 Physics Solved Question Paper 2005

    Multiple Choice QuestionsShort Answer Type

    31. Define dispersive power of the material of a prism. The refractive indices of a prism for violet, yellow and red colours are 1.632,1.620 and 1.613 respectively. Calculate the dispersive power of the material of the prism. 
    1361 Views
    Answer
    32. A convex lens and a plane mirror are kept at a distance of 10 cm as shown in the diagram. Parallel rays incident on the convex lens after reflection from the mirror form an image at the optical centre. Complete the ray diagram and find out the focal length of the lens. 
    360 Views
    Answer
    33. Explain why light waves can be polarised but sound waves cannot. Describe a method by which a plane polarised light can be distinguished from a partially polarised light. 
    469 Views
    Answer
    34. Sunglasses have curved surfaces, but their power is zero. Why ?
    750 Views
    Answer
    Advertisement
    35. Define magnifying power of an optical instrument. An astronomical refracting telescope consists of two lenses of focal length 75 cm and 5 cm. Calculate the magnifying power of the telescope when the final image is formed at a distance of 25 cm from the eye. 
    589 Views
    Answer
    36. What is Compton scattering ? Mention the important conclusion drawn from the phenomenon of Compton scattering.
    1106 Views
    Answer
    37.

    The threshold wavelength of tungsten is 2400 Å.  

    When tungsten is illuminated with light of wavelength 1600 Å, find :

    (i) Work function

    (ii) Maximum kinetic energy of the emitted electron

    (iii) Stopping potential.

    420 Views
    Answer
    38. In a Thomson set-up for finding e/m, the electrons are accelerated through a potential difference of 2500 V. The electrons then enter a region of crossed electric and magnetic fields of magnitudes 3.6 x 104 V/m and 1.2 x 10 3 T respectively and pass through undeviated. Calculate the e/m of an electron. 
    279 Views
    Answer
    Advertisement
    Advertisement
    Zigya App

    39. In a hydrogen atom a transition of electrons take place from 3rd orbit to 2nd orbit. Calculate the wavelength of the emitted photon. To which spectral series will this photon belong ? 

    Rydberg constant (R) = 1.097 x 107 m-1

    For hydrogen atom Z = 1, n1 = 2, n2 = 3


    1 over straight lambda space equals space R Z squared space open parentheses 1 over n subscript 1 squared space minus space 1 over n subscript 2 squared close parentheses space space space space space space equals space 1.097 space x space 10 to the power of 7 space x space left parenthesis 1 right parenthesis squared open parentheses 1 over 2 squared space minus space 1 over 3 squared close parentheses space space space space equals space 1.097 space x space 10 to the power of 7 space open parentheses fraction numerator 9 space minus space 4 over denominator 36 end fraction close parentheses space space space space equals space 1.097 space x space 10 to the power of 7 space x space 5 over 36 space space space space equals space 0.15 space x space 10 to the power of 7 1 over straight lambda space space equals space 1.5 space straight x space 10 to the power of 6 space straight lambda space equals space fraction numerator 1 over denominator 1.5 space straight x space 10 to the power of 6 end fraction space space space space equals space 0.66 space straight x space 10 to the power of negative 6 end exponent space equals space 6600 space straight x space 10 to the power of negative 10 end exponent space space space equals space 6600 space straight A with straight o on top 


    Transition of electrons from 3rd orbit to 2nd orbit forms Balmer series and lie in the visible part of spectrum.
    354 Views
  • Switch Icon Switch
    • Advertisement
    40. Define half-life of a radioactive substance. Establish a relationship between half-life T and decay constant λ.
    925 Views
    Answer
    Advertisement

    NCERT Solutions
    Textbook Solutions | Additional Questions

    Flag Popup Icon
    Flag it
    Submit
    Flag Popup Icon
    Switch to
    flexipad
    Share It Icon
    Share it
    Share It
    Share it