Ray Optics

What type of image does this lens form?

• Virtual image
• Real Image
• No Image

A 25.0 m object is placed 30.0 m from a convex lens, which has a focal length of 5.0 m. What is the distance of the image?

• 6 m

• 7 m

• 8 m

• 9 m

Which figure represents the path light takes through a converging lens?

• 
• 
• 
• 

A hollow convex lens of glass will behave like

• convex lens

• concave lens

• glass plate

• mirror

A concave lens forms the image of an object such that the distance between the object and image is 10 cm and the magnification produced is 1/4. The focal length of the lens will be : __________

• 8.6 cm

• 6.2 cm

• 10 cm

• 4.4 cm

A real image is formed by a a convex lens, then it is put in contact with a concave lens and again a real image is formed. This image is : ______________

• shift towards the lens system

• shift away from the lens system

• remain in its original position

• shift to infinity

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. the power of the combination is : ______

• - 1.5 D

• -6.5 D

• + 6.5 D

• + 6,67 D

A plano–convex lens fits exactly into another plano-concave lens. Their plane surface are parallel to each other. If the lenses are made of different materials, what is the focal length of combination? Given that:

𝑅 = Radius of curvature of the curved portion

𝜇1 = refractive index of material of plano-concave lens

𝜇2= refractive index of material of plano-convex lens

• $\frac{R}{\left(\mu2-\mu1\right)}$

• $\frac{R}{\left(\mu1-\mu2\right)}$
  

• $\frac{R}{\left(\mu2-1\right)}$

• $\frac{R}{\left(\mu1-1\right)}$

Two plano-concave lenses (1 and 2) made of glass of refractive index 1.5 have radii of curvature 25𝑐𝑚 and 20 𝑐𝑚 respectively. They are placed in contact with their curved surface towards each other and the space between them is filled with a liquid of refractive index 4/3. Then the combination is

• Convex of focal length 70 𝑐𝑚

• Concave of focal length 9.5 𝑐𝑚

• Concave of focal length 66.6 𝑐𝑚

• Convex of focal length 9.5 𝑐𝑚

A concave lens is in contact with a convex lens. The magnitude of the ratio of their focal lengths is 2/3. Their equivalent focal length is 30 𝑐𝑚. What are their individual focal lengths respectively?

• −75,50

• -10, 15

• 75,50

• −15,10