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tamaranim1 [39]
4 years ago
8

In the autocollimation experiment of Sec. 3.5, a thin convex lens is placed 25 cm from a pinhole that acts as a point source of

light. A plane mirror placed 20 cm behind the lens reflects the light back through the lens, and the reflected light forms a sharp spot beside the pinhole. What is the focal length of the lens (in cm)?
Physics
1 answer:
Lera25 [3.4K]4 years ago
4 0

Answer:

25 cm

Explanation:

Since, in the question it is given that the final image after reflection through the convex lens and then the reflection by the plane mirror is formed at the pinhole itself.

This means that the pinhole must be at the focus of the convex lens, such that the lens makes the ray perpendicular to the mirror and hence focal length of the lens = 25 cm.

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A person carries a box of 100 kg. What is the weight of the box? (g= 9.8 m/s2)​
aliina [53]

Answer:

980 newton

Explanation:

100×9.8 = 980

8 0
3 years ago
Considera que en tu casa tienes un televisor de 110 W, si pasa encendido 4 horas diarias, Cuál será la energía consumida durante
rjkz [21]

Answer:

 E = 13.2 kWh

,     Cost = $ 10.8

Explanation:

We can look for the consumed energy from the expression of the power

      P = W / t

The work is equal to the variation of the kinetic energy, for which

       P = E / t

       E = P t

       

look for the energy consumed in one day and multiply by the days of the month in the month

      E = 110 4 30

      E = 13200 W h

       E = 13.2 kWh

the cost of this energy is

    Cost = 0.9 12

    Cost = $ 10.8

4 0
3 years ago
Read 2 more answers
The energy of a photon of light is __________ proportional to its frequency and __________ proportional to its wavelength.
icang [17]

Answer:

D) directly, inversely

Explanation:

The energy of a photon of light is directly proportional to its frequency and inversely proportional to its wavelength.

Frequency is the number of waves that passes through a point per unit of time.

Wavelength is the is the distance between successive crests or troughs on a wave.

 Mathematically, frequency is related to wavelength and velocity using;

             Energy   =  h x f

                      where h is the Planck's constant

                                  f is the frequency

         

                   Since c  = f ∧

where f is the frequency of the wave

           ∧ is the wavelength of the wave

           c is the speed of light

So;

                 f  = c/∧

  Therefore;

                E  = \frac{h c}{wavelength}

From the equation, we see an inverse relationship between E and wavelength and a direct one with frequency.

           

6 0
3 years ago
Young's Modulus refers to changes in the a Volume b- Length c- Body layers
Novosadov [1.4K]

Explanation:

Young' modulus is the ratio of normal stress to the longitudinal strain. Mathematically, it is given by :

Normal stress is given by force per unit area. Longitudinal strain is the change in length per unit original length.

The mathematical definition of Young's modulus is given by :

Y=\dfrac{F/A}{\Delta L/L}..........(1)

Where

\Delta L is the change in length

F is the force

A is the area of cross section

So, the Young's modulus refers to the change in length of the object. Hence, the correct option is (b) "length".

8 0
3 years ago
Based on observations, the speed of a jogger can be approximated by the relation v 5 7.5(1 2 0.04x) 0.3, where v and x are expre
castortr0y [4]

Answer:

solution:

to find the speed of a jogger use the following relation:  

V

=

d

x

/d

t

=

7.5

×m

i

/

h

r

...........................(

1

)  

in Above equation in x and t. Separating the variables and integrating,

∫

d

x

/7.5

×=

∫

d

t

+

C

or

−

4.7619  

=

t

+

C

Here C =constant of integration.   

x

=

0  at  t

=

0

, we get:  C

=

−

4.7619

now we have the relation to find the position and time for the jogger as:

−

4.7619  =

t

−

4.7619

.

.

.

.

.

.

.

.

.

(

2

)

Here

x  is measured in miles and  t  in hours.

(a) To find the distance the jogger has run in 1 hr, we set t=1 in equation (2),    

     to get:

      = −

4.7619  

      =  

1

−

4.7619

      = −

3.7619

  or  x

=

7.15

m

i

l

e

s

(b) To find the jogger's acceleration in   m

i

l

/

differentiate  

     equation (1) with respect to time.

     we have to eliminate x from the equation (1) using equation (2).  

     Eliminating x we get:

     v

=

7.5×

     Now differentiating above equation w.r.t time we get:

      a

=

d

v/

d

t

       =

−

0.675

/

      At  

      t

=

0

      the joggers acceleration is :

       a

=

−

0.675

m

i

l

/

        =

−

4.34

×

f

t

/  

(c)  required time for the jogger to run 6 miles is obtained by setting  

        x

=

6  in equation (2).  We get:

        −

4.7619

(

1

−

(

0.04

×

6  )

)^

7

/

10=

t

−

4.7619

         or

         t

=

0.832

h

r

s

6 0
3 years ago
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