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NEET Physics Solved Question Paper 2008

Multiple Choice Questions

41.
If λ₁and λ₂ are the wavelengths of the first members of the Lyman and Paschen series respectively, then λ₁ : λ₂ is

1 : 3

1 : 30

7 : 50

7 : 108

7 : 108

For first-line of Lyman series

n₁ = 1 and n₂ = 2

$∴ \frac{1}{λ_{1}} = R (\frac{1}{1^{2}} - \frac{1}{2^{2}}) = R (1 - \frac{1}{4}) = \frac{3 R}{4}$

For first line of Paschen series

n₁ = 3 and n₂ = 4

$∴ \frac{1}{λ_{2}} = R (\frac{1}{3^{2}} - \frac{1}{4^{2}}) = R (\frac{1}{9} - \frac{1}{16}) = \frac{3 R}{4} = \frac{7 R}{144} ∴ \frac{λ_{1}}{λ_{2}} = \frac{7 R}{144} \times \frac{4}{3 R} = \frac{7}{108}$

42.

The activity of a radioactive sample decreases to
(1/3)^rd of its original value in 3 days. Then, in 9 days its activity will become

(1/27) of the original value
(1/9) of the original value
(1/18) of the original value
(1/3) of the original value

43.

Identify the operation performed by the circuit given below

NOT
AND
OR
NAND

44.

The working of which of the following is similar to that of a slide projector?

Electron microscope
Scanning electron microscope
Transmission electron microscope
Atomic force microscope

45.

In a transistor, the collector current is always less than the emitter current because

collector side is reverse biased and the emitter side is forward biased
a few electrons are lost in the base and only remaining ones reach the collector
collector being reverse biased attracts less electron
collector side is forward biased and emitter side is reverse biased

46.

The specific rotation of a sugar solution is 0.5 deg m²/kg. 200 kg-m^-3 of impure sugar solution is- taken in a sample polarimeter tube of length 20 cm and optical rotation is found to be 19°. The percentage of purity of sugar is

47.

To a germanium crystal, an equal number of aluminium and indium atoms are added. Then

it remains an intrinsic semiconductor
it becomes a n-type semiconductor
it becomes a p-type semiconductor
it becomes an insulator

48.

Maximum velocity of the photoelectrons emitted by a metal surface is 1.2x10⁶ ms^-1. Assuming the specific charge of the electron to be 1.8 x10¹¹ C kg^-1, the value of the stopping potential in volt will be