Intro to Thin Lenses

Q. A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen

1. Complete image will be formed of same intensity
2. Complete image will be formed of decreased intensity
3. Half the image will disappear
4. Half image will be formed of same intensity

Q. Which method is used to minimize the chromatic aberration in the spherical lenses?

1. By using concave lens
2. By using convex lens
3. By combining concave and convex mirrors
4. By combining concave and convex lenses

Q. Figure shows variation of magnification m (produced by a thin convex lens) and distance $v$ of image from the pole of the lens. Which of the following statements are correct?

1. Focal length of the lens is equal to intercept on $v$-axis.
2. Focal length of the lens is equal to inverse of slope of the line.
3. Magnitude of intercept on $m$-axis is equal to unity.
4. None

Q. Figure shows two convex lenses A and B, each made up of three different transparent materials. The number of images formed, of an object kept on the principal axis of each lens will be

1. 3 and 3
2. 3 and 1
3. 1 and 1
4. 3 and 2

Q. A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen

1. Half the image will disappear
2. Complete image will be formed of same intensity
3. Half image will be formed of same intensity
4. Complete image will be formed of decreased intensity

Q. Assertion :The focal length of an equiconvex lens placed in air is equal to radius of curvature of either face. Reason: For an equiconvex lens radius of curvature of both the faces is same.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. A convex lens of focal length f is placed at origin. Object is placed on negative x-axis anywhere between $-\infty$ to $+\infty$. Choose correct graph between 'u' and 'v'.

1. 
2. 
3. 
4. 

Q. A convex lens is made of 3 layers of glass of 3 different materials as in the figures. A point object is placed on its axis . The number of images of the object are

1. 1
2. 2
3. 3
4. 4

Q. Two thin convex lenses of focal length $f_1$ and $f_2$ are separated by a horizontal distance $d$ (where $d<f_1,d<f_2)$ and their centers are displaced by a vertical separation $△$ as shown in the figure.
Taking the origin of coordinates $O$ at the center of the first lens, the $x$ and $y$ coordinates of the focal point of this lens system, for a parallel beam of rays coming from the left, are given by

1. $x=\frac{f_1{f}_2}{f_1+f_2},y=\Delta$
2. $x=\frac{f_1{f}_2+d(f_1-d)}{f_1+f_2-d},y=\frac{\Delta (f_1-d)}{f_1+f_2-d}$
3. $x=\frac{f_1(f_2+d)}{f_1+f_2-d},y=\frac{\Delta }{f_1+f_2}$
4. $x=\Delta ,y=\frac{\Delta (f_1-d)}{f_1+f_2-d}$

Q. Two thin convex lenses of focal lengths $f_1$ and $f_2$ are separated by a horizontal distance $d(d<f_1$ and $d<f_2)$ and their centers are displaced by a vertical separation as shown in figure. A parallel beam of rays coming from left. Take the origin of coordinates $O$ at the center of first lens.
Find the x-coordinates in the same problem from the focal point of this lens system.

1. $\frac{d(f_1-d)+f_1{f}_2}{(f_1+f_2-d)}$
2. $\frac{f_1{f}_2}{(f_1+f_2-d)}$
3. $\frac{d(f_1-d)}{(f_1+f_2-d)}$
4. $\frac{2d(f_1+d)-f_1{f}_2}{(f_1+f_2-d)}$

Q. A double convex lens of focal length f is cut into 4 equivalent parts. One cut is perpendicular to the axis and the other is parallel to the axis of the lens. The focal length of each part is :

1. $f/2$
2. $f$
3. $2f$
4. $4f$

Q. In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the screen is adjusted to get a clear image of the object. A graph between the object distance $u$ and the image distance $v$, from the lens, is plotted using the same scale for the two axes. A straight line passing through the origin and making an angle of ${45}^o$ with the $x$-axis meets the experimental curve at P. The coordinates of $P$ will be

1. $(2f,2f)$
2. $(\frac{f}{2},\frac{f}{2})$
3. $(f,f)$
4. $(4f,4f)$.

Q. The lens in spectacles can be approximated to thin lens.

1. True
2. False

Q. The lens in spectacles can be approximated to thin lens.

1. True
2. False

Q. A convex lens of focal length f is placed at origin. Object is placed on negative x-axis anywhere between $-\infty$ to $+\infty$. Choose correct graph between 'u' and 'v'.

1. 
2. 
3. 
4. 

Q. The lens in spectacles can be approximated to thin lens.

1. True
2. False

Q. In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the scree is adjusted to get a clear image of the object. A graph between the object distance u and the image distance v, from the lens, is plotted using the same scale for the two axes. A straight line passing through the origin and making an angle of ${45}^o$ with the x-axis meets the experimental curve at P. The coordinates of P will be :

1. $(2f,2f)$
2. $(\frac{f}{2},\frac{f}{2})$
3. $(f,f)$
4. $(4f,4f)$