CBSE Class 12 Physics Past Paper Questions PDF

CBSE Class 12 Physics Question Paper Solution 55/1/1 MARKING SCHEME – PHYSICS Q....

CBSE Class 12 Physics Question Paper Solution 55/1/1 MARKING SCHEME – PHYSICS Q. Total Value Points/ Expected answers Marks No. Marks 1 1 1 [Note: i) Deduct ½ mark, if arrows are not shown. ii) do not deduct any mark, if charges on the plates are not shown] 2 No Change 1 1 3 Threshold frequency equals the minimum frequency of incident radiation (light) that can cause photoemission from a given photosensitive surface. (Alternatively) The frequency below which the incident radiations cannot cause the 1 photoemission from photosensitive surface. 1 OR Intensity of radiation is proportional to (/ equal to) the number of energy quanta (photons) per unit area per unit time. 4 d𝜇𝑟 = tan 300 = (where d𝜇𝑟 is the retractive index of rarer ½ medium w.r.t denser medium) µd = v= = = x m/s ½ [Note- Also accept if a student solves it as follows) µ = tan ip µ = tan 300 = ½ 1 = = x m/s ½ (Note: Award this one mark if a student just writes the formula but does not solve it.) 5 The waves beyond 30 MHz frequency penetrate through the Ionosphere/ are not 1 reflected back. OR 1 Transmitted Power and Frequency ½+½ SECTION - B 6 Calculation of Power dissipation in two combinations 1 +1 𝑉2 𝑉2 ½ 𝑅1 = 𝑃1 , 𝑅2 = 𝑃 , 2 𝑉2 𝑃1 𝑃2 Ps = Rs = 𝑃1 +𝑃2 1 1 1 ½ = +𝑃 Ps 𝑃1 2 1 1 1 𝑃1 + 𝑃2 =R + = 𝑉2 Rp R2 1 ½ 1