2. Determine the image distance and image height for a 5.0cm tall object placed

Question

2. Determine the image distance and image height for a 5.0cm tall object placed 45.0cm from a double concave lens having a focal length with a magnitude of 15.0cm. Draw the ray diagram.

3. Two converging lenses, with the focal length f1= 9cm and f2=16cm are placed 39cm apart. An object is placed 51cm in front of the first lens.

a) Find the position of the final image relative to the second lens.

b) Find the magnification of the final image

5. A lens has one concave surface with a radius of curvature RA= 6.0cm and one convex surface with radius of curvature RB=8.0cm. It has an index of refraction of 1.2.

a) Is this a converging or diverging lens when use in air?

b) If this lens is used under water, which has an index of refraction of 1.33, would the focal length change?

6. A red laser is emitted by a waterproof pointer inside a tank of water. Water has an index of refraction of 1.33.

a) What is the minimum angle that the laser light ray would need to strike the surface of the water for it to be trapped inside the water?

b) If the light ray travels upward and strikes the surface of the water at 45-degrees to the normal line, what angle will the beam make with the normal when it emerges into air?

c) Would the angle found in part-b be exactly the same if a green laser were used instead of red? If not, would the angle be larger, or smaller and why?

7. A converging lens, focal length 7.5cm, is places 10cm away from a 0.5cm tall object.

a) Make a ray diagram of the lens with the focal points and optical axis included. Locate the image using the 3 principle rays. Indicate in the diagram where a person’s eye might be, if they can see the image.

b) Is the image upright or inverted?

c) How far from the lens does the image appear?

d) What is the image size?

8. Draw a ray diagram of a concave mirror when the object is closer to the mirror than the focal length. Is the image real or virtual? Is the image larger or smaller? Is the image upright or inverted?

9. A small plastic sphere is charged to -10nC and is held 1cm above a small glass bead at rest on a table. The bead has a mass of 15mg and a charge of +10nC. Will the glass bead “lead up” to the plastic sphere?

10. Two small spheres in a vacuum are 2m apart and carry identical charges. How large is the charge on each if the spheres experience a force of 3N?

11. Calculate the strength and direction of the electric field due to a point charge of 5nC at a distance of 4mm from the charge. What fore does the electric field exert on a point charge of -0.28µC

12. A dipole formed between a +1.6x10-19 C and -1.6x10-19 C charge is 0.128nm long. If the dipole is in a uniform electric field of 4.5x105N/C then what is the magnitude of torque that works on the dipole when the angle between E and p is 25 degrees.

13. Two point charges of 3µC and 1.5x10-20 kg are 2.5 nm apart. If one of the point charges were fixed, then how fast would the other point charge be moving when it reaches infinity?

Explanation / Answer

The height of bulb is h = 5.0cm

     object distance is u = 45cm

     focal length is f = 15 cm

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Let v is the image distance then

     (1/f) = 1/u + 1/v   

     1/v =  1/f - 1/u

           =1 /15 cm - 1/ 45 cm

       then we get v= 22.5 cm  

   The magnification is m = size of image /size of object =- image distance (v) / object distance(u)

                                    size of image = -v*5 cm / u

                                                          =-(22.5cm)*5 cm / 45 cm

                                                          = -2.5 cm

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