Sunday, June 06, 2021

Why do roads look darker on rainy nights

 A dark rainy night can already be a dangerous situation due to the slick road surface and the reduced ability to see at a distance, but it also seems like it makes the roads darker, making them harder to navigate.

When you are driving down a dark road, the light from your headlights scatters off the rough road surface and some of it is reflected back to you.  When the surface is wet, it becomes more reflective.  More light is reflected away and less light is scattered back to you.





Friday, July 15, 2011

Laser Toys for Cats

In response to this post, I have a question.  My cats love playing with the red dot of a laser pointer but I am concerned about the safety and health of their eyes.  I don't point it at their eyes...but they do stare at it for over 10 seconds and sometimes run into the path of it. I am wondering if a LED pinpoint flashlight (one that focuses as small as a laser beam would)....would be safer? If so where could I purchase one?

There is no risk to your cats' eyes from staring at the spot a laser pointer makes on the ground, even if they stare at it for a long time.  The only concern would be if you aimed the laser pointer directly into their eyes and held it there a while.  And it is likely your cat would find this unpleasant and turn its eyes away.

If you are still concerned, a LED or incandescent flashlight would be even safer since the beam will not focus as tightly even if the beam gets directly in your cats eyes.

Unfortunately, I am not sure where you would find a LED "pinpoint" flashlight.  Typically you want a flashlight to have a wide beam and a laser pointer to have a small beam, so that is the way they are manufactured.  Also, lasers are inherently narrow beamed while it would require additional components to make an LED have a small beam.

You could try one of the cat toys that keep the beam moving, like this one at Think Geek.




Monday, May 09, 2011

Who will I marry?

Who will I marry? -Leanne

Great question Leanne! From a social pyschology point of view, you are most likely to form a relationship with somebody you are frequently exposed to. Take a look around, maybe you already met your future spouse!

Saturday, December 25, 2010

Nuclear Plants

Does some nuclear waste have to be stored for 100's of years?
Have some states banned nuclear plants?
Which are more expensive to build, nuclear or coal plants?

Spent nuclear fuel rods from nuclear plants remain highly radioactive and need to be stored until they are safe. Some elements can remain radioactive for thousands of years. Currently, used nuclear fuel is stored at the nuclear plant facilities as an interim solution to disposal.

Several U.S. states have a ban on (new) nuclear plants, including California, Connecticut, Hawaii, Kentucky, Maine, Massachusetts, Minnesota, Oregon, Wisconsin and West Virginia.

It typically costs more to build a nuclear plant than a coal plant.

Tuesday, September 21, 2010

What are photons and how do they differ from electrons?

The photon is an elementary massless particle representing a quantum of electromagnetic radiation, or light. Albert Einstein was instrumental in developing the concept of the particle nature of light and, in fact, received his Nobel Prize for using the quantum nature of light to explain the photoelectric effect.

Electrons are also elementary particles. Unlike photons, they have mass and charge. Electrons are also sub-atomic particles (along with protons and neutrons).

Wednesday, September 15, 2010

Why does my son always stare off at lights?

Why does my son always stare off at the light, Lamps, ceiling fixtures, any kind of light fixtures?

I am assuming that your son is an infant. This is more of a question about child psychology than optical phenomena and I am afraid I don't know much about child behavior. Scanning a few websites, though, I see many parents commenting on how their babies love to stare at lights (see this link). I would guess that your son stares at lights because they are fascinating. Bright shiny sources of light are a new experience for him.

Saturday, September 12, 2009

Light Bulbs in your Field of View

I've read your response about incandescent lights being generally eye safe to look at but I still have some questions. Is a clear bulb safe even if its within your field of view? If you were watching TV would it be damaging to the eyes to have the image of the filament sit on your periphery? I understand the eye moves while watching TV so it wouldn't stay on the same location on the retina. Also what if it was right next to your central vision, say a clear bulb next to your television, would it cause damage then? if you were watching the TV for hours upon hours?. I've tried to find the answer to these questions about how dangerous the clear incandescent light bulbs are but there doesn't seem to be much information regarding it, especially light damage on the peripheral of your eye.

An incandescent lightbulb in your field of view over an extended period of time is generally safe to view, whether it is in the center of your view or in the peripheral. Your eyes will provide you with some feedback if it is not good. If your eyes squint, or you feel discomfort, then that is your body telling you that maybe it isn't a good idea.