Question 1 :
The focal length of a combination of lenses formed with lenses having powers of $+2.50\ D$ and $-3.75\ D$ will be

Question 2 :
Which of the following parts of compound microscope is used for minutefocussing

Question 3 :
Assertion: Rainy clouds appear dark from below. Reason: There is not sufficient light which can be scattered by these clouds.

Question 4 :
An object is placed on the principal axis of a convex mirror of focal length 15 cm. If the distance of the object from the mirror is 30 cm, determine the image distance

Question 5 :
Three lenses have a combined power of $2.7 D$. If the powers of two lenses are $2.5 D$ and $1.7 D$ respectively, find the focal length of the third lens.

Question 6 :
When a ray of light traveling in a (A) Medium, is incident at the surface of a (B) Medium such that angle if incidence is (C) than the critical angle for the pair of media, the ray is totally reflected back into the (D) medium. This phenomenon is called total internal reflection.

Question 7 :
Assertion: If optical density of a substance is more than that of water then the mass density of substance can be less than water. Reason: Optical density and mass density are not related.

Question 9 :
When a wave travels from one medium to another, the quantity which will not change is its

Question 11 :
Rectilinear motion of light in a medium is caused due to:

Question 13 :
The maximum illumination on a screen at a distance of $2\ m$ from a lamp is $25\ lux$. The value of total luminous flux emitted by the lamp

Question 14 :
The rising and setting of sun appear red because of : 

Question 16 :
When total internal reflection occurs from a prism,________of incident light is reflected back to denser medium. Fill on the blank. 

Question 19 :
The frequency of a light wave in a material is $2\times 10^{14} Hz$ and wavelength is $5000\overset {\circ}{A}$. The refractive index of material will be :

Question 20 :
A concave mirror is placed on a horizontal table with its axis directed vertically upwards. Let O be the pole of the mirror and C be its center of curvature. A point object is placed at C, whose real image is also formed at C. If the mirror is now filled with water, the image will be<br>

Question 21 :
The parameter that determines the brightness of a light source sensed by an eye is

Question 22 :
A double convex lens has radii of curvature of 1 m and 2m, What should be the refractive index of the material such that the focal length of the lens is 50 cm?

Question 23 :
The focal lengths of the objective and eye-lens of a microscope are $1\, cm$ and $5\, cm$ respectively. If the magnifying power for the relaxed eye is $45$, then the length of the tub is

Question 24 :
An equilateral prism deviates a ray through $45^{\circ}$ for the two angles of incidence differing by $20^{\circ}.$ The angle of incidence is<br/>

Question 25 :
A lamp hanging $4$ metres above the table is lowered by $1$ metre. The illumination on the table:

Question 26 :
A convex lens forms an image of an object on ascreen. The height of the image is 9 cm. The lens is now displaced until animage is again obtained on the screen. The height of this image is 4 cm.Thedistance between the object and the screen is 90 cm.

Question 27 :
A hollow double concave lens is made of very thin transparent material. It can be filled with air or either of two liquid $L_{1}$ or $L_{2}$ having refractive indices $\mu_{1}$ and $\mu_{2}$ respectively $(\mu_{2} &gt; \mu_{1} &gt; 1)$. The lens will diverge a parallel beam of light if it is filled

Question 28 :
When the object is placed 4 cm from the objective of microscope, the final image formed coincides with the object. The final image is at the least distance of distinct vision (24 cm). If the focal length of eye piece is 8 cm then the focal length of objective is

Question 29 :
A astronomical telescope has objective and eyepiece of focal lengths $40\ cm$ and $4\ cm$ respectively. To view an object $200\ cm$ away from the objective, the lenses must be separated by a distance:

Question 30 :
A motor car is fitted with a convex driving mirror of focal length 20cm. A second motor car 2.8m behind the first car is overtaking speed of 15 $ { ms }^{ -1 }$. The speed of the image of the second car as seen in the mirror of the first is&#160; :

Question 32 :
A plano-convex lens, when silvered at its plane surface is equivalent to a concave mirror of focal length 28 cm. When its curved surface is silvered and the plane surface is not silvered, it is equivalent to a concave mirror of focal length 10 cm, then the refractive index of the material of the lens is :

Question 33 :
A plano convex lens of focal length 30 cm has its plane surface silvered. An object is placed 40 cm from the lens on the convex side. The distance of the image from the lens is:

Question 34 :
A glass slab of thickness 18 cm and refractive index$\dfrac{3}{2}$ is placed on a printed matter. The normal shift of the printed matter is

Question 35 :
<br>Concave and convex lenses, each have the same focal length $20 cm$ and they are put in contact to form a combination lens. This combination lens is used to view an object of $5 cm$ length, kept at a distance $20 cm$ from the lens combination. As compared to the object the image will be<br>

Question 36 :
Assertion: Focal length of a combination of same type of lenses in contact is always less than focal length of any of the lenses. Reason: The focal length f of a combination of lenses of focal lengths&#160;<span class="MathJax_Preview"><span class="MathJax"><span class="math"><span class="mrow"><span class="msubsup"><span class="mi">f<span class="mn">1<span class="MJX_Assistive_MathML">f1&#160;and&#160;<span class="MathJax_Preview"><span class="MathJax"><span class="math"><span class="mrow"><span class="msubsup"><span class="mi">f<span class="mn">2<span class="MJX_Assistive_MathML">f2&#160;in contact is given by$\dfrac{1}{F}=\dfrac{1}{F_1}+\dfrac{1}{F_2}$<span class="MathJax"><span class="MJX_Assistive_MathML">1f=