2. UV is responsible for sun tanning. Find the wavelength (in nm) of a UV photon whose energy is 6.4 x 10^19 Joules. What part of the UV spectrum is this?
3. Surfaces A and B are irradiated and are observed to emit IR, and UV light respectively. What electromagnetic wave would the incident radiation be for surface A and for surface B? Explain.
4. Why do Astronomers say that viewing an event like supernova or any celestial object such as star is looking back in time?
5. How long ago in years did the supernova occurred?
6. The brightest star in the night sky is Sirius. It is estimated to be 8.3 x 10^16 meters from earth. When we look at this star, how far back in time are we seeing it? Express your answers in years. Assume 1 yr. = 365.25 days
2007-06-26 02:31:02 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Are you even going to *try* to do your own homework?
2007-06-26 02:33:19 · answer #1 · answered by ZikZak 6 · 3⤊ 0⤋
The questions aren't really interrelated, so i'll answer question #1 only:
Bats and owls, though both nocturnal, use different methods to see in the dark. Bats use echolocation, a method that works very much like radar. Bats emit high-pitched sounds and make then bounce off objects. The bat's huge ears pick up these sounds and its brain determines the distance and direction of the object the sound bounced off from.
Owls, on the other hand, use vision. Its pupils let in more light than a human eye would allow, absorbing more of the little available light, therefore making the owl more capable of seeing in the dark than humans.
Owls and bats see better in the dark because they hunt at night. They will need 'seeing devices' better in navigating through the darkness than a human eye.
oh, and yes, Megachiroptera bats actually have good vision (except for the egyptian fruit bat). Most Megachiroptera bats rely on their sense of smell to find their food.
2007-06-26 03:17:11 · answer #2 · answered by vyrill21 3 · 0⤊ 0⤋
I'll give you the easy ones.
1) The retina of a lot of animals is 'reflective'. It bounces the light back thru the rods and cones so they pass them twice - so they can absorb twice as much light. This can be seen by shining a flashlight into the eyes of a person at night from a good distance - then compare that to shining a flashlight into the eyes of a cat from a distance - the cats eyes will appear to light up because it is reflecting the light back.
4) It takes 8 minutes for the light of the sun to reach earth. So, the sunlight you see was 'born' 8 minutes ago. Hence, you are looking at the past. If we see a star explode, since the closest star is about 7 light years away, we would be witnessing an event that happened at least 7 years ago.
6) Since the speed of light is 299,792,458 m / s, 8.3 x 10^16 divided by this number is 276858199 seconds. 365.25 days/year = 8766 hours/year = 31557600 seconds/year.
So, 276858199 seconds / 31557600 seconds/year = 8.7731 years.
2007-06-26 02:51:35 · answer #3 · answered by Anonymous · 0⤊ 0⤋
My layman's understanding is that while owls have eyes which are designed to let in a maximum of star and other night light, the bats use a kind of radar, and do not have good eyesight.
Shame on you for not even trying to research your home work your own self. You seem to be too lazy to even separate the questions into the different categories. How pathetic.
2007-06-26 02:34:46 · answer #4 · answered by Anonymous · 0⤊ 0⤋
I am not going to answers your physics questions.
Bats have poor night vision. They navigate at night by echolocation -- sound waves. Never heard the phrase "blind as a bat"?
Owls have large forward facing eyes and highly sensitive retinas so they capture a lot of light.
2007-06-26 02:35:04 · answer #5 · answered by Sandy G 6 · 1⤊ 0⤋
owls and bats are naturally nocturnal, where as humans are naturally diurnal. Therefore we do not need to have superb night vision, where as owls, have larger eyes and their eyes refract light. Bats do not have great vision, but they use sonar, much like a dolphins do as well.
2007-06-26 02:48:54 · answer #6 · answered by Anonymous · 0⤊ 0⤋
owls also have sonar similar to bats with good night vision
super nova occured about 4 billions years ago
2007-06-26 02:48:40 · answer #7 · answered by Worm Brain 2 · 0⤊ 0⤋
bats and owl actually don hav a good night vision, they are almost blind.they move by using the principle of the reflection of sound wave. they emit high frequency sound wave to the surrounding. if the wave collide with an object, it will refect back to the bats and owl. thier ears recieve the reflected sound wave. as a result they will know tat in front of them hav some objects and they need to move to other direction.
2007-06-26 02:54:57 · answer #8 · answered by Anonymous · 0⤊ 0⤋
Owls have big eyes. Bats do not have good vision; they use sonar. Haven't you ever heard the expression "blind as a bat"?
2007-06-26 02:34:09 · answer #9 · answered by Dr. R 7 · 1⤊ 0⤋
ANSWER FOR # 1 they have better vision because they are nocturnal
2007-06-26 02:33:37 · answer #10 · answered by Erin 2 · 0⤊ 0⤋