In some observation the observed object distance (Separation between indicos of object needle and mirror) is `30.2 cm` and the observed imager distane is `19.9cm` Using index correction from previous two questions estimate the focal length of the concave mirror .
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A convex mirror has radius of curvature of 20 cm. An object is placed at such a distance from the mirror that the size of image is exactly half that o
Correct Answer - C f=10 , `m=f/(f-u)` `m=1/2 rArr u=-10`
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The radius of curvature of a converging mirror is 30 cm. At what distance from the mirror should an object be placed
Correct option is (d) Between 0 cm and 15 cm
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A magnetic needle is free to oscillate in a uniform magnetic field as shown in the figure. The magnetic moment of magnetic needle `7.2Am^(2)` and mome
Here, `T=("Number of revolutions")/("Time taken")=(5)/(10)=0.5s` `" " M=7.2Am^(2),I=6.5xx10^(-6)kgm^(2)` `As, " " T=2pi sqrt((I)/(MB)) or T^(2)=4pi^(2)(I)/(MB)` The magnetude of the magnetic field is `" " B=(4pir^(2)I)/(MT^(2))=(4xx(3.14)^(2)xx6.5xx10^(-6))/(7.2xx(0.5)^(2))=1.42xx10^(-4)T`
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To find index error for u when a knitting needle of length `20.0cm` is adjusted between pole and object needle the separation between the indices of o
Index error (Excess reading) = Obsorved reading Actual reading `=20.2 - 20.0 = 0.2cm` .
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To find index error v when the same knitting needle is adjusted between the pole and the image needle the separation between the indices of image need
Correct Answer - B `e = 19.9 cm - 20.0 cm = - 0.1 cm`
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A short linear object of length b lies along the axis of a concave mirror or focal length f at a distance u from the pole of the mirror. The size of t
Correct Answer - B (b) Using mirror formula, `1/v+1/(-u)=1/(-f)` Multiplying with u, `u/v=(-u)/f)+1=(f-u)/f` `therefore` Magnification, m=`v/u=(f/(f-u))` Now, `abs(dv)=m^(2)abs(du)` Sizze of image=`(f/(f-u))^(2)`cdotb`
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Assertion In front of a concave mirror, a point object is placed between focus and centre of curvature. If a glass slab is placed between object and m
Correct Answer - C (c) Glass slab will shift the object towards mirror. If it comes between pole and focus the image will become virtual.
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The distance between object and the screen is D. Real images of an object are formed on the screen for two positions of a lens separated by a distance d. The ratio between the sizes of two images will be:
d(object and screen) = D = u + v and d = v – u Thus, d + D = 2v ∴ v = [(d + D) / 2] and u = [(D...
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The distance of an object from a spherical mirror is equal to the focal length of the mirror. Then the image:
Correct Answer - B Image formation by concave mirror when object is real & placed at focus f. forms image at infinity but not in other cases.
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The distance between an object and its doubly magnified image by a concave mirror is: [Assume `f`= focal length]
Correct Answer - A For `m=2` `m=(v)/(u)=2` `V=-2u` ………………..`(i)` `(1)/(f)=(1)/(v)+(1)/(u) rArr (1)/(f)=(1)/(-2u)+(1)/(u)` `rArr (1)/(f)=(1)/(2u) rArr u=(f)/(2)` `& v=-f` Distance between object `&` image `=f+f//2=3f//2` For `m=-2` `m=-(v)/(u)=-2` `v=2u` `rArr (1)/(f)=(1)/(2u)+(1)/(u) rArr...
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