Answer:  Light of frequency 5 x 1014 HZ liberates electrons with energy 2.3 x 10-19from a certain metallic surface. 
Explanation:
 
        
             
        
        
        
Bohr's equation for the change in energy is

where
h = Planck's constant
c == the velocity of light
λ = wavelength.
The velocity is related to wavelength and frequency, f, by
c = fλ
Let us examine the given answers on the basis of the given equations.
a. As λ increases, f decreases and ΔE decreases.
     TRUE
b. As λ increases, f increases and ΔE increases.
    FALSE
c. As λ increases, f increases and ΔE decreases.
    FALSE
Answer:  
As the wavelength increases, the frequency decreases and energy decreases.
 
        
        
        
Answer:
0.00903 rad
0.00926 rad
6.268\times 10^{-6}
Explanation:
s = Diameter of the object
r = Distance between the Earth and the object
Angle subtended is given by

For the Moon

The angle subtended by the Moon is 0.00903 rad
For the Sun

The angle subtended by the Sun is 0.00926 rad
Area ratio is given by

The area ratio is 
 
        
             
        
        
        
Answer:
a)   v_average = 11 m / s, b)  t = 0.0627 s
, c)    F = 7.37 10⁵ N
, d)   F / W = 35.8
Explanation:
a) truck speed can be found with kinematics
          v² = v₀² - 2 a x
The fine speed zeroes them
            a = v₀² / 2x
            a = 22²/2 0.69
            a = 350.72 m / s²
The average speed is
            v_average = (v + v₀) / 2
            v_average = (22 + 0) / 2
            v_average = 11 m / s
b) The average time
           v = v₀ - a t
           t = v₀ / a
           t = 22 / 350.72
           t = 0.0627 s
c) The force can be found with Newton's second law
              F = m a
              F = 2100 350.72
              F = 7.37 10⁵ N
.d) the ratio of this force to weight
              F / W = 7.37 10⁵ / (2100 9.8)
              F / W = 35.8
.e) Several approaches will be made:
- the resistance of air and tires is neglected
- It is despised that the force is not constant in time
- Depreciation of materials deformation during the crash