The beam from a small laboratory laser typically has an intensity of about
. Assuming that the beam is composed of plane waves, calculate the amplitudes of the electric and magnetic fields in the beam.
Strategy
Use the equation expressing intensity in terms of electric field to calculate the electric field from the intensity.
A 60-kW radio transmitter on Earth sends its signal to a satellite 100 km away (
[link] ). At what distance in the same direction would the signal have the same maximum field strength if the transmitter’s output power were increased to 90 kW?
In three dimensions, a signal spreads over a solid angle as it travels outward from its source.
Strategy
The area over which the power in a particular direction is dispersed increases as distance squared, as illustrated in the figure. Change the power output
P by a factor of (90 kW/60 kW) and change the area by the same factor to keep
the same. Then use the proportion of area
A in the diagram to distance squared to find the distance that produces the calculated change in area.
Solution
Using the proportionality of the areas to the squares of the distances, and solving, we obtain from the diagram
Significance
The range of a radio signal is the maximum distance between the transmitter and receiver that allows for normal operation. In the absence of complications such as reflections from obstacles, the intensity follows an inverse square law, and doubling the range would require multiplying the power by four.
The energy carried by any wave is proportional to its amplitude squared. For electromagnetic waves, this means intensity can be expressed as
where
I is the average intensity in
and
is the maximum electric field strength of a continuous sinusoidal wave. This can also be expressed in terms of the maximum magnetic field strength
as
and in terms of both electric and magnetic fields as
The three expressions for
are all equivalent.
Conceptual questions
When you stand outdoors in the sunlight, why can you feel the energy that the sunlight carries, but not the momentum it carries?
The amount of energy (about
) is can quickly produce a considerable change in temperature, but the light pressure (about
) is much too small to notice.
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
hello. autism is a umbrella term. autistic kids have different disorder overlapping. for example. a kid may show symptoms of ADHD and also learning disabilities.
before treatment please make sure the kid doesn't have physical disabilities like hearing..vision..speech problem. sometimes these
Jharna
continue..
sometimes due to these physical problems..the diagnosis may be misdiagnosed.
treatment for autism.
well it depends on the severity.
since autistic kids have problems in communicating and adopting to the environment.. it's best to expose the child in situations where the child
Jharna
child interact with other kids under doc supervision.
play therapy.
speech therapy.
Engaging in different activities that activate most parts of the brain.. like drawing..painting. matching color board game.
string and beads game.
the more you interact with the child the more effective
Jharna
results you'll get..
please consult a therapist to know what suits best on your child.
and last as a parent. I know sometimes it's overwhelming to guide a special kid.
but trust the process and be strong and patient as a parent.
Jharna
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