Question 1 :
Scientists identify the elements that are burning in the stars by using which of the following devices?
Question 2 :
Find the power (with sign) of a concave lens of focal length $20cm$.<br/>
Question 3 :
When the length of a microscope tube increases, its magnifying power :<br/>
Question 5 :
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 7 :
If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image
Question 8 :
Assertion: The images formed by total internal reflections are much brighter than those formed by mirrors or lenses
Reason: There is no loss of intensity in total internal reflection.
Question 9 :
What will be the colour of sky as seen from the earth, if there were no atmosphere
Question 10 :
A concave mirror and aconverging glass with $(\mu =1.5)$ both have a focal length of $3cm $ when in air. When they are in water $\left(\mu =\dfrac{4}{3}\right)$ their new focal lengths are
Question 11 :
An object is placed at a distance $2 f$ from the pole of a convex mirror of focal length $f$. The linear magnification is:
Question 12 :
A straight line graph is obtained by plotting sine of angle of incidence versus sine of angle of refraction. The slope of this graph represents :
Question 13 :
A thin equiconvex glass lens of refractive index $1.5$ has power of $5D$. When the lens is immersed in a liquid of refractive index $\mu$, it acts as a divergent lens of focal length $100 \,cm$. The value of $\mu$ of liquid is
Question 16 :
Air has refractive index $1.0003$. Find the thickness of air column which will contain one more wavelength of yellow light of $6000$ $A^0$ than in same thickness of vacuum.
Question 18 :
A pin which is 2 cm long is placed at a distance of 16 cm from a convex lens. Assuming it to be perpendicular to the principal axis, find the position of the image if the focal length of the lens is 12 cm.
Question 19 :
The angle between the incident ray and the normal is called ________.<br>
Question 20 :
The image of a square hole in a screen illuminated by light is obtained on another screen with the help of a converging lens. The distance of the hole from the lens is $40\ cm$. If the area of the image is nine times that of the hole, the focal length of the lens is :
Question 21 :
A convex lens of focal length $f$ is placed somewhere in between the object and a screen. The distance between object and screen is $x$. If magnification produced is $m$, the focal length of the lens is:
Question 23 :
Assertion: Although the surfaces of goggle lenses are curved, it does not have any power.
Reason: In case of goggle, both the curved surfaces have equal radii of curvature and have center of curvature on the same side.
Question 24 :
The distance between an object and its doubly magnified image by a concave mirror is: [ Assume $f$ = focal length]
Question 25 :
An object of length $2\ cm$ is placed at distance $1.5f$ from a concave mirror where $'f'$ is its focal length. Find the length of the image.
Question 26 :
What happens when a ray of light is made to fall on a mirror along the normal?<br/>
Question 27 :
A solid transparent sphere has a small opaque dot at its centre. When observed from outside, the apparent position of the dot will be
Question 28 :
The reflecting surface is given by $y = \dfrac{10L}{\pi} \sin \dfrac{\pi x}{5L}$. The co-ordinates of the point where a horizontal ray becomes vertical after reflection is:
Question 29 :
The focal lengths of the objective and the eyepiece of a compound microscope are $2.0\ cm$ and $3.0\ cm$, respectively. The distance between the objective and the eyepiece is $15.0\ cm$. The final image formed by the eyepiece is at infinity. The two lenses are thin. The distance, in $cm$, of the object and the image produced by the objective, measure from the objective lens, are respectively.
Question 30 :
The angle of minimum deviation for a ${75^ \circ }$ prism of dense glass is found to be ${45^ \circ }$ when in air and ${15^ \circ }$ when immersed in certain liquid. The refractive index of the liquid is :
Question 31 :
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 $(\mu_{2} > \mu_{1} > 1)$. The lens will diverge a parallel beam of light if it is filled
Question 32 :
A monochromatic light passes through a glass slab $\left (\mu = \dfrac {3}{2}\right )$ a thickness $90\ cm$ in time $t_{1}$. If it takes $t_{2}$ to travel the same distance through water $\left (\mu = \dfrac {4}{3}\right )$. The value of $(t_{1} - t_{2})$ is :
Question 33 :
An object 2 cm high is placed at a distance of 16 cm from a concave mirror, which produces a real image 3 cm high. What is the focal length of the mirror?
Question 34 :
The focal length of a thin biconvex lens is 20 cm. when an object is moved from a distance of 25 cm in front of it to 50 cm, the magnification of its image changes from $m_{25}$ to $m_{50}$. The ratio of $m_{25}$ to $m_{50}$ is :
Question 35 :
An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2 m away from the bulb is $5\times10^{-4}$ phot $(lumen/cm^2)$. The line joining the bulb to the point makes an angle of $60^o$ with the normal to the surface. The luminous intensity of the bulb in candela (candle power ) is
