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Program to determine focal length of a spherical mirror
  • Difficulty Level : Easy
  • Last Updated : 12 Apr, 2021

Write a program to determine the focal length of a spherical mirror.
Focal length is the distance between the center of the mirror to the principal foci. In order to determine the focal length of a spherical mirror we should know the radius of curvature of that mirror. The distance from the vertex to the center of curvature is called radius of curvature. 
The focal length is half the radius of curvature. 
Formula :
 

F =   ( R / 2 )      for concave mirror
F = - ( R / 2 )      for convex mirror

Examples : 
 

For a convex mirror
Input : R = 30 
Output : F = 15


For a convex mirror
Input : R = 25
Output : F = - 12.5

 

 

C++




// C++ program to determine
// the focal length of a
// of a spherical mirror
#include<iostream>
using namespace std;
 
// Determines focal length
// of a spherical concave
// mirror
float focal_length_concave(float R)
{
    return R / 2 ;
}
 
// Determines focal length of a
// spherical convex mirror
float focal_length_convex(float R)
{
    return - ( R / 2 ) ;
}
 
// Driver function
int main()
{
    float R = 30 ;    
    cout << "Focal length of spherical"
         << "concave mirror is : "
         << focal_length_concave(R)
         << " units\n";
    cout << "Focal length of spherical"
         << "convex mirror is : "
         << focal_length_convex(R)
         << " units";
    return 0;
}

Java




// Java program to determine
// the focal length of a
// of a spherical mirror
import java.util.*;
import java.lang.*;
 
public class GfG{
    // Determines focal length
    // of a spherical concave
    // mirror
    public static float focal_length_concave(float R)
    {
        return R / 2 ;
    }
 
    // Determines focal length of a
    // spherical convex mirror
    public static float focal_length_convex(float R)
    {
        return - ( R / 2 ) ;
    }
     
    // Driver function
    public static void main(String argc[])
    {
        float R = 30 ;
         
        System.out.print("Focal length of" +
                         "spherical concave"+
                         "mirror is : "+
                         focal_length_concave(R) +
                         " units\n");
                         
        System.out.println("Focal length of"+
                           "spherical convex"+
                           "mirror is : "+
                           focal_length_convex(R) +
                           " units");
    }
}
 
/* This code is contributed by Sagar Shukla */

Python




# Python3 program to determine
# the focal length of a
# of a spherical mirrorr
 
# Determines focal length of
# a spherical concave mirror
def focal_length_concave(R):
    return R / 2
 
# Determines focal length of
# a spherical convex mirror
def focal_length_convex(R):
    return - ( R/ 2 )
 
# Driver function
R = 30 ;
print("Focal length of spherical concave mirror is :",
        focal_length_concave(R)," units")
print("Focal length of spherical convex mirror is : ",
        focal_length_convex(R)," units")

C#




// C# program to determine the focal
// length of a of a spherical mirror
using System;
 
class GfG {
     
    // Determines focal length of a
    // spherical concave mirror
    public static float focal_length_concave(float R)
    {
        return R / 2 ;
    }
 
    // Determines focal length of a
    // spherical convex mirror
    public static float focal_length_convex(float R)
    {
        return - ( R / 2 ) ;
    }
     
    // Driver function
    public static void Main(String[] argc)
    {
        float R = 30 ;
        Console.Write("Focal length of" +
                      "spherical concave" +
                      "mirror is : " +
                      focal_length_concave(R) +
                      " units\n");
                         
        Console.Write("Focal length of" +
                      "spherical convex" +
                      "mirror is : " +
                      focal_length_convex(R) +
                      " units");
    }
}
 
/* This code is contributed by parashar */

PHP




<?php
//PHP program to determine
// the focal length of a
// of a spherical mirror
 
// Determines focal length
// of a spherical concave
// mirror
 
function focal_length_concave($R)
{
    return $R / 2 ;
}
 
// Determines focal length of a
// spherical convex mirror
function focal_length_convex($R)
{
    return - ( $R / 2 ) ;
}
 
// Driver function
 
    $R = 30 ;    
    echo "Focal length of spherical",
              "concave mirror is : ",
            focal_length_concave($R),
                          " units\n";
                           
    echo "Focal length of spherical",
              " convex mirror is : ",
             focal_length_convex($R),
                            " units";
 
// This code is contributed by ajit
?>

Javascript




<script>
 
// javascript program to determine
// the focal length of a
// of a spherical mirror
 
// Determines focal length
    // of a spherical concave
    // mirror
    function focal_length_concave(R)
    {
        return R / 2 ;
    }
   
    // Determines focal length of a
    // spherical convex mirror
    function focal_length_convex(R)
    {
        return - ( R / 2 ) ;
    }
 
// Driver Function
 
         let R = 30 ;
           
        document.write("Focal length of" +
                         "spherical concave"+
                         "mirror is : "+
                         focal_length_concave(R) +
                         " units" + "<br/>");
                           
        document.write("Focal length of"+
                           "spherical convex"+
                           "mirror is : "+
                           focal_length_convex(R) +
                           " units");
      
     // This code is contributed by susmitakundugoaldanga.
</script>

Output : 
 

Focal length of spherical concave mirror is 15 units
Focal length of spherical convex mirror is -15 units

 

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