1. A biconvex lens of focal length f forms a circular image of sun of radius r in focal plane. Then

(A) πr^2 ∝ f

(B) πr^2 ∝ f^2

(C) if lower half part is covered by black sheet, then area of the image is equal to πr^2/2

(D) if f is doubled, intensity will increase

2.MgSO-4 on reaction with NH-4OH and Na-2HPO-4 forms a white crystalline precipitate. What is its formula?

(A) Mg(NH-4)PO-4

(B) Mg-3(PO-4)-2

(C) MgCl-2.MgSO-4

(D) MgSO-4

3. For x > 0, Lim[(Sin)^(1/x)+(1/x)^sinx)] is

(x -> 0)

(A) 0

(B) -1

(C) 1

(D) 2

## Tuesday, September 25, 2007

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