Suppose a camera’s exposure is correct when the lens has a focal length of 8.0 mm. Will the picture be overexposed, underexposed, or still correct if the focal length is “zoomed” to 16.0 mm without changing the diameter of the lens aperture? Explain.
A camera has a circular aperture immediately behind the lens. Reducing the aperture diameter to half its initial value will
Make the image blurry.
Cut off the outer half of the image and leave the inner half unchanged.
Make the image less bright.
All the above.
Explain your choice.
Suppose you wanted special glasses designed to let you see underwater without a face mask. Should the glasses use a converging or diverging lens? Explain.
A red card is illuminated by red light. What color will the card appear? What if it’s illuminated by blue light?
The center of the galaxy is filled with low-density hydrogen gas that scatters light rays. An astronomer wants to take a picture of the center of the galaxy. Will the view be better using ultraviolet light, visible light, or infrared light? Explain.
A friend lends you the eyepiece of his microscope to use on your own microscope. He claims the spatial resolution of your microscope will be halved, since his eyepiece has the same diameter as yours but twice the magnification. Is his claim valid? Explain.
A diffraction-limited lens can focus light to a spot on a screen. Do the following actions make the spot diameter larger, make it smaller, or leave it unchanged?
Decreasing the wavelength of the light.
Decreasing the lens diameter.
Decreasing the lens focal length.
Decreasing the lens-to-screen distance.
To focus parallel light rays to the smallest possible spot, should you use a lens with a small f-number or a large f-number? Explain.
An astronomer is trying to observe two distant stars. The stars are marginally resolved when she looks at them through a filter that passes green light with a wavelength near 550 nm. Which of the following actions would improve the resolution? Assume that the resolution is not limited by the atmosphere.
Changing the filter to a different wavelength. If so, should she use a shorter or a longer wavelength?
Using a telescope with an objective lens of the same diameter but a different focal length. If so, should she select a shorter or a longer focal length?
Using a telescope with an objective lens of the same focal length but a different diameter. If so, should she select a larger or a smaller diameter?
Using an eyepiece with a different magnification. If so, should she select an eyepiece with more or less magnification?