1
JEE Main 2021 (Online) 31st August Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
An object is placed at the focus of concave lens having focal length f. What is the magnification and distance of the image from the optical centre of the lens?
A
1, $$\infty$$
B
Very high, $$\infty$$
C
$${1 \over 2}$$, $${f \over 2}$$
D
$${1 \over 4}$$, $${f \over 4}$$
2
JEE Main 2021 (Online) 31st August Morning Shift
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
A sample of a radioactive nucleus A disintegrates to another radioactive nucleus B, which in turn disintegrates to some other stable nucleus C. Plot of a graph showing the variation of number of atoms of nucleus B versus time is :

(Assume that at t = 0, there are no B atoms in the sample)
A
JEE Main 2021 (Online) 31st August Morning Shift Physics - Atoms and Nuclei Question 103 English Option 1
B
JEE Main 2021 (Online) 31st August Morning Shift Physics - Atoms and Nuclei Question 103 English Option 2
C
JEE Main 2021 (Online) 31st August Morning Shift Physics - Atoms and Nuclei Question 103 English Option 3
D
JEE Main 2021 (Online) 31st August Morning Shift Physics - Atoms and Nuclei Question 103 English Option 4
3
JEE Main 2021 (Online) 31st August Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at centre, when a current I passes through coil:
A
$${{{\mu _0}IN} \over {2(b - a)}}{\log _e}\left( {{b \over a}} \right)$$
B
$${{{\mu _0}I} \over 8}\left[ {{{a + b} \over {a - b}}} \right]$$
C
$${{{\mu _0}I} \over {4(a - b)}}\left[ {{1 \over a} - {1 \over b}} \right]$$
D
$${{{\mu _0}I} \over 8}\left( {{{a - b} \over {a + b}}} \right)$$
4
JEE Main 2021 (Online) 31st August Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A body of mass M moving at speed V0 collides elastically with a mass 'm' at rest. After the collision, the two masses move at angles $$\theta$$1 and $$\theta$$2 with respect to the initial direction of motion of the body of mass M. The largest possible value of the ratio M/m, for which the angles $$\theta$$1 and $$\theta$$2 will be equal, is :
A
4
B
1
C
3
D
2
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