Answer:
<u>B. the stars of spectral type A and F are considered reasonably to have habitable planets but much less likely to have planets with complex plant - or animal - like life.</u>
Explanation:
The appropriate spectral range for habitable stars is considered to be "late F" or "G", to "mid-K" or even late "A". <em>This corresponds to temperatures of a little more than 7,000 K down to a little less than 4,000 K</em> (6,700 °C to 3,700 °C); the Sun, a G2 star at 5,777 K, is well within these bounds. "Middle-class" stars (late A, late F, G , mid K )of this sort have a number of characteristics considered important to planetary habitability:
• They live at least a few billion years, allowing life a chance to evolve. <em>More luminous main-sequence stars of the "O", "B", and "A" classes usually live less than a billion years and in exceptional cases less than 10 million.</em>
• They emit enough high-frequency ultraviolet radiation to trigger important atmospheric dynamics such as ozone formation, but not so much that ionisation destroys incipient life.
• They emit sufficient radiation at wavelengths conducive to photosynthesis.
• Liquid water may exist on the surface of planets orbiting them at a distance that does not induce tidal locking.
<u><em>Thus , the stars of spectral type A and F are considered reasonably to have habitable planets but much less likely to have planets with complex plant - or animak - like life.</em></u>
Answer:
Given
Frequency (f) = 3Hz
Wavelength = 9 m
Speed = ?
Explanation:
we know
Speed = wavelength * frequency
= 9*3
= 27 m/ s
Answer:
C. microscope
Explanation:
A simple microscope is magnifying glass, an ordinary double convex lens having a short focal length that produces virtual and erect image.
Answer: 9*10^15 N
Force=kqq/r^2
F=[(9*10^9)(1)(1)]/.001^2=9.0*10^15
according to PBS learning media on a roller coaster energy changes from potential to kinetic energy and back again many times over the course of a ride kinetic energy is energy that an object has as a result of its motion.
roller coaster system is greatest at the bottom of the largest downhill slope on the track typically at the bottom of the lift Hill
so at the bottom
