Question 1 :
An object 20 cm from lens, has a virtual image at 10 cm from the object. The power of the lens is
Question 2 :
A manufacturer uses a concave lens instead of a convex lens in a magnifying glass by mistake. What will be the effect on the working of the lens?
Question 3 :
Assertion: Rainy clouds appear dark from below.
Reason: There is not sufficient light which can be scattered by these clouds.
Question 6 :
The sun appears red at the time of sun-rise and sun-set. This is because:
Question 7 :
Fine beam of light entering through a small hole in a dark room illuminates the particles in its path. Identify the effect associated with this process.<br/>
Question 8 :
A convex lens of focal length $12.5cm$ is used as a simple microscope. When the image is formed at infinite. Magnification is ________ (Near point for the normal vision is $25cm$)
Question 9 :
Consider the following statements A and B andidentify the correct choice<br>A) For a given value of angle of incidence, theangle of deviation produced by a prismincreases with increasing of refractive index ofthe prism<br>B) Angle of deviation produced by a thin prismis independent of angle of incidence<br>
Question 10 :
A convex lens is used to form an image of an object on a screen, If the upper half of the lens is blackened so that it becomes opaque.Then :
Question 11 :
Assertion: A concave mirror and convex lens both have the same focal length in air. When they are submerged in water, they will have same focal length. <br>Reason: The refractive index of water is smaller than the refractive index of air.
Question 12 :
A ray of light takes grazing incidence on the first face of a prism and the emergent ray is normal to the ${2}^{nd}$ face of the prism. If D is angle of deviation then the refracting angle of the prism is equal to<br/>
Question 15 :
If eyepiece lens of a compound microscope is moved a little away from objective lens without changing positions of object and objective lens, then
Question 16 :
What is the power of the lens, if the far point of a short sighted eye is $200\ cm$?
Question 17 :
Time taken by the sunlight to pass through a window of thickness 4mm whose refractive index is 1.5 is
Question 18 :
The image formed behind a mirror and that formed behind a magnifying glass
Question 19 :
For which of the following colour, the magnifying power of a microscope will be maximum
Question 20 :
When light goes from a denser to a rarer medium the angle of refraction is:
Question 21 :
A converging lens of refractive index $1.5$ kept in a liquid medium having the same refractive index. What would be the focal length of the lens in this medium?<br/>
Question 22 :
Change in the direction of light when it passes from one medium to another is called ............
Question 23 :
Scientists identify the elements that are burning in the stars by using which of the following devices?
Question 24 :
Magnifying power of simple microscope is 6, when image is formed at distance of distinct vision, the focal length of simple microscope is :
Question 25 :
The power of a lens being $+4$ dioptres suggests that it is a
Question 26 :
Which of the following statements are true?<br>a. The spectrum of sunlight has 7 colors<br>b. Spectrum is seen due to bending of lights of different colors at different angles with respect to the incident ray through a prism<br>c. Red light bends the least whereas violet light bends the maximum<br>d. Rainbow is an example of dispersion of light
Question 27 :
Real Image is always erect. Is the above statement True or False?<br/>
Question 28 :
Two lens of focal lengths $-20 cm$ and $+10 cm$ are put in combination. Find the power of the combination.
Question 29 :
Which color should be used to increase the resolving power of a microscope
Question 30 :
The power of a lens having a focal length of $1 cm$ is :<br/>
Question 31 :
Intensity of refracted ray of light will be ________ than that of the incident light. Fill in the blank. 
Question 32 :
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 33 :
A thin convex lens of focal length $10\ cm$ is placed in contact with a concave lens of same material and of same focal length. he focal length of combination will be
Question 35 :
The incident ray, the normal at the point of incidence and the refracted ray:
Question 37 :
A convergent beam of light converges to a point 20 cm behind a concave lens on the principal axis. An inverted image of the same size is formed. An inverted image of the same size is formed. Then the focal length of the lens is then<br/>
Question 38 :
A thin convergent glass lens $(\mu_g = 1.5)$ has a power of +5.0 D. When this lens is immersed in a liquid of refractive index $\mu$, it acts as a divergent lens of focal length 100 cm. The value of $\mu$ must be
Question 39 :
In which of the following instruments is the final image virtual?
Question 40 :
If the focal length of a magnifying glass is 2.5 cm, itcan magnify an object
Question 41 :
An electric bulb of luminous intensity I is suspended at a height h from the center of the table having a circular surface diameter $2r$, the illuminace at the center of the circular disc will be
Question 43 :
Two thin lenses of focal lengths 20 cm and 25 cm are placedin contact. The effective power of the combination is :
Question 44 :
An equi-biconvex lens of focal power $10D$ is cut into two equal parts perpendicular to its axis. If its refractive index is $1.5$, the radius of curvature of one of the parts is
